Proton conductor production method thereof, and electrochemical device using the same

ABSTRACT

A proton conductor mainly contains a carbonaceous material derivative, such as, a fullerene derivative, a carbon cluster derivative, or a tubular carbonaceous material derivative in which groups capable of transferring protons, for example, —OH groups or —OSO 3 H groups are introduced to carbon atoms of the carbonaceous material derivative. The proton conductor is produced typically by compacting a powder of the carbonaceous material derivative. The proton conductor is usable, even in a dry state, in a wide temperature range including ordinary temperature. In particular, the proton conductor mainly containing the carbon cluster derivative is advantageous in increasing the strength and extending the selection range of raw materials. An electrochemical device, such as, a fuel cell, that employs the proton conductor is not limited by atmospheric conditions and can be of a small and simple construction. The proton conductor may contain a polymer in addition to the carbonaceous material derivative, which conductor can be formed, typically by extrusion molding, into a thin film having a large strength, a high gas permeation preventive ability, and a good proton conductivity.

RELATED APPLICATION DATA

[0001] The present application is a continuation-in-part of U.S. patentapplication Ser. No. 09/396,866 (Attorney Docket No. P99,1588) filed onSep. 15, 1999.

[0002] The present application claims priority to Japanese PatentApplication No. H11-204038 filed on Jul. 19, 1999, Japanese PatentApplication No. P2000-058116 filed on Mar. 3, 2000, and Japanese PatentApplication No. P2000-157509 filed on May 29, 2000. The above-referencedJapanese patent applications are incorporated herein by reference to theextent permitted by law.

BACKGROUND OF THE INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a proton conductor, a productionmethod thereof, and an electrochemical device using the protonconductor.

[0005] 2. Description of the Prior Art

[0006] In recent years, as a polymer solid-state electrolyte type fuelcell has been used to power cars, there has been known a fuel cell usinga polymer material having a proton (hydrogen ionic) conductivity such asa perfluorosulfonate resin (for example, Nafion® produced by Du Pont).

[0007] As a relatively new proton conductor, there has also been known apolymolybdate having large amount of hydrated water such asH₃Mo₁₂PO₄₀.29H₂O or an oxide having a large amount of hydrated watersuch as Sb₂O₆.5.4H₂O.

[0008] The above-described polymer material and hydrated compounds eachexhibit, if placed in a wet state, a high proton conductivity at atemperature near ordinary temperature.

[0009] For example, the reason why the perfluorosulfonate resin canexhibit a very high proton conductivity even at ordinary temperature isthat protons ionized from sulfonate groups of the resin are bonded(hydrogen-bonded) with moisture already entrapped in a polymer matrix ina large amount, to produce protonated water, that is oxonium ions(H₃O⁺), and the protons in the form of the oxonium ions can smoothlymigrate in the polymer matrix.

[0010] More recently, there has been also developed a proton conductorhaving a conduction mechanism quite different than that of each of theabove-described proton conductors.

[0011] That is to say, it has been found that a composite metal oxidehaving a perovskite structure, such as, SrCeO₃ doped with Yb, exhibits aproton conductivity without use of moisture as a migration medium. Theconduction mechanism of this composite metal oxide has been consideredsuch that protons are conducted while being singly channeled betweenoxygen ions forming a skeleton of the perovskite structure.

[0012] The conductive protons, however, are not originally present inthe composite metal oxide but are produced by the following mechanism:namely, when the perovskite structure contacts the steam contained in anenvironmental atmospheric gas, water molecules at a high temperaturereact with oxygen deficient portions which have been formed in theperovskite structure by doping Yb or the like, to generate protons.

[0013] The above-described various proton conductors, however, have thefollowing problems.

[0014] The matrix material such as the above-identifiedperfluorosulfonate resin must be continuously placed in a sufficientlywet state during use in order to keep a high proton conductivity.

[0015] Accordingly, a configuration of a system, such as, a fuel cellusing such a matrix material, requires a humidifier and variousaccessories, thereby giving rise to problems in enlarging the scale ofthe system and raising the cost of the system.

[0016] The system using the matrix material has a further problem thatthe range of the operational temperature must be limited for preventingthe freezing or boiling of the moisture contained in the matrix.

[0017] The composite metal oxide having the perovskite structure has aproblem that the operational temperature must be kept at a hightemperature of 500° C. or more for ensuring an effective protonconductivity.

[0018] In this way, the related art proton conductors have the problemsthat the atmosphere dependence on the performance of each conductorbecomes high, and more specifically, moisture or stream must be suppliedto the conductor to ensure the performance of the conductor, andfurther, the operational temperature of the conductor is excessivelyhigh or the range of the operational temperature is limited.

SUMMARY OF THE INVENTION

[0019] A first object of the present invention is to provide a protonconductor which is usable in a wide temperature range including ordinarytemperature and has a low atmosphere dependence, that is, it requires nomoisture despite whether or not the moisture is a migration medium; toprovide a method of producing the proton conductor; and to provide anelectrochemical device that employs the proton conductor. To meet thisobjective, the proton conductor includes a proton conductor materialthat at least has number of functional groups so as to be capable oftransferring hydrogen protons between the functional groups of theproton conductor material. The proton conductor material includes a widevariety of carbonaceous materials, examples of which are described ingreater detail below with respect to the various illustrativeembodiments of the present invention, such as, the first, second, thirdand fourth proton conductors, production methods and electrochemicaldevices thereof.

[0020] A second object of the present invention is to provide a protonconductor which exhibits a film formation ability while keeping theabove-described performance, to be thereby usable as a thin film havinga high strength, a gas permeation preventive or impermeable performance,and a good proton conductivity, to provide a method of producing theproton conductor, and to provide an electrochemical device using theproton conductor.

[0021] The present invention provides a first proton conductor mainlycontaining a fullerene derivative obtained by introducing a number offunctional groups so as to be capable of transferring protons betweenthe functional groups of the fullerene derivative. The fullerenederivative includes a fullerene molecule or a plurality of fullerenemolecules that each contain the functional groups so as to provide thefullerene derivative with the desirable proton conductivity propertiesas discussed and will be discussed in greater detail below.

[0022] The present invention also provides a first method of producing aproton conductor, including the steps of: producing a fullerenederivative by introducing functional groups so as to be capable oftransferring protons as previously discussed; and compacting a powder ofthe fullerene derivative into a desired shape.

[0023] The present invention also provides a first electrochemicaldevice including: a first electrode, a second electrode, and a protonconductor held between the electrodes, wherein the proton conductormainly contains a fullerene derivative as described above.

[0024] According to the first proton conductor of the present invention,since the conductor mainly contains the fullerene derivative having aproton transfer capability, protons are easily transferred or conducted,even in a dry state, and further, the protons can exhibit a highconductivity in a wide temperature range (at least in a range of about160° C. to −40° C.) that includes ordinary temperatures. While the firstproton conductor of the present invention has a sufficient protonconductivity even in a dry state, it can also have a proton conductivityin a wet state. The moisture may come from the outside.

[0025] According to the first production method of the presentinvention, since the production method includes the steps of: producinga fullerene derivative by introducing functional groups as discussed andmolding a substance comprising the fullerene derivative, the protonconductor can be efficiently produced having the above-described uniqueperformance without use of any binder resin. The term “molding” meansmolding in a shape of film, pellet or the like. Therefore, compaction orfiltration or other like techniques are preferably available forproducing the proton conductor.

[0026] According to the first electrochemical device of the presentinvention, since the proton conductor is held between the first andsecond electrodes, the first electrochemical device can eliminate theneed for a humidifier and the like which are necessary for known fuelcells that require moisture as a migration medium so as to enhanceproton conductivity. Therefore, the device construction of the presentinvention has an advantageously smaller and more simplifiedconstruction.

[0027] The present invention also provides a second proton conductorthat includes a polymer material in addition to the fullerene derivativeas previously discussed.

[0028] The present invention also provides a second method of producinga proton conductor, including the steps of: producing a fullerenederivative by introducing functional groups as discussed above; andmixing the fullerene derivative with a polymer material and forming themixture into a desired shape, such as, a thin film.

[0029] The present invention also provides a second electrochemicaldevice including: a first electrode, a second electrode, and a protonconductor held between the electrodes, wherein the proton conductormainly contains a fullerene derivative as previously discussed, and apolymer material.

[0030] According to the second proton conductor of the presentinvention, since the conductor contains the fullerene derivative and apolymer material, it can exhibit not only an effect (high protonconductivity) comparable to that of the first proton conductor, but alsoa film formation ability unlike the first proton conductor that onlycontains the fullerene derivative. The second proton conductor, thus,can be effectively used as a thin film having a high strength, a gaspermeation preventive ability, and a high proton conductivity.

[0031] According to the second production method of the presentinvention, since the method includes the steps of: producing a fullerenederivative, and mixing the fullerene derivative with a polymer materialthereby molding the mixture into a desired shape, such as, a thin film,it can efficiently produce the proton conductor having the above uniqueperformance in the form of a thin film. The term “molding” means moldingin a desired shape by squeezing-out, compacting, coating or the like asfurther detailed above.

[0032] According to the second electrochemical device of the presentinvention, since the proton conductor that contains the fullerenederivative is held between the first and second electrodes, the secondelectrochemical device can exhibit an effect comparable to that of thefirst electrochemical device, since the proton conductor also containsthe polymer material, the second electrochemical device can exhibit thesame desirable effects as the second proton conductor.

[0033] The present invention also provides a third proton conductor thatincludes a carbon cluster derivative which has a number of functionalgroups so as to be capable of transferring protons between thefunctional groups of the carbon cluster derivative. The carbon clusterderivative includes a cluster or a plurality of clusters as its basematerial. The clusters each mainly or substantially contain a number ofcarbon atoms, preferably, on order of several to several hundred carbonatoms.

[0034] The present invention also provides a third method of producing aproton conductor, including the steps of: producing clusters of carbonatoms by an arc discharge method using a carbon-based electrode; andsubjecting the carbon powder of the clusters to acid treatment or thelike, to introduce functional groups to the carbon powder so as to formthe carbon cluster derivative that is capable of transferring protons aspreviously discussed.

[0035] The present invention also provides a third electrochemicaldevice including: a first electrode, a second electrode, and a protonconductor held between the electrodes, wherein the proton conductormainly contains a carbon cluster derivative obtained by introducingfunctional groups to a cluster or a number of clusters that are the basematerial of the carbon cluster derivative as discussed.

[0036] The present invention has uniquely discovered that it is requiredto form proton conductive paths (migration sites or channels) in thecarbonaceous material of the proton conductor as much as possible forimparting a good proton conductivity to the proton conductor. To meetsuch a requirement, it is necessary to introduce two or more functionalgroups that are capable of transferring protons, for example, on asurface of each of the clusters or a number of clusters, such as, anumber of carbon clusters of the carbon cluster derivative. The carboncluster is preferably made as small as possible. In this way, the carbonclusters can exhibit a desirable proton conductivity when combined inbulk to form the carbon cluster derivative of the proton conductor.

[0037] The cluster of the present invention generally means an aggregatein which atoms on order of several hundred are bonded or aggregated toeach other. The aggregate improves the proton conductivity and alsoensures a sufficient film strength while maintaining its chemicalproperty to be thereby easily formed into a layer. The “cluster mainlyor substantially containing carbon atoms” means an aggregate in which anumber of carbon atoms, preferably on order of several hundred, areclosely bonded to each other irrespective of the typically knownmolecular bonding that occurs between carbon atoms. Although this typeof cluster contains a large number of carbon atoms, it is not limitedonly to carbon atoms and may include a variety of other atoms within itsaggregate structure. Hereinafter, a cluster aggregate that contains alarge number of carbon atoms—yet may also contain other atoms—isreferred to as a “carbon cluster”.

[0038] According to the third proton conductor of the present invention,the conductor mainly contains a carbon cluster derivative that has achemical structure which allows protons to be easily transferred asdiscussed, even in a dry state, with a result that the third protonconductor can exhibit effects, such as, a desirable proton conductivity,which are similar to those of the first proton conductor. In addition,the carbon cluster derivative may include clusters or carbon clustersthat contain a variety of different carbonaceous materials—examples ofwhich are discussed below.

[0039] According to the third production method of the presentinvention, since the production method produces the clusters or carbonclusters by making use of the arc discharge method using a carbon basedelectrode and subjects the carbon clusters or clusters to at least acidtreatment, it can efficiently produce the carbon cluster derivative ofthe proton conductor having the above-described unique properties at alow cost.

[0040] According to the third electrochemical device of the presentinvention, since the above proton conductor is held between the firstand second electrodes, the third electrochemical device can exhibiteffects similar to those of the first electrochemical device.

[0041] The present invention also provides a fourth proton conductormainly containing a tubular carbonaceous material derivative thatincludes functional groups so as to be capable of transferring protonsbetween the functional groups of the tubular carbonaceous materialderivative in a similar fashion as protons are transferred on the protonconductor of the previously discussed embodiments, namely the first,second, and third proton conductors, production methods, andelectrochemical devices thereof.

[0042] The present invention also provides a fourth method of producinga proton conductor that includes the steps of preparing a halogenated ornon-halogenated tubular carbonaceous material as a raw material; andintroducing functional groups onto the tubular carbonaceous material bysubjecting the material to hydrolysis and/or acid treatment or plasmatreatment so as to form the tubular carbonaceous material derivative.

[0043] The present invention also provides a fourth electrochemicaldevice that includes a first electrode, a second electrode and a protonconductor that is positioned between the electrodes wherein the protonconductor mainly contains the tubular carbonaceous material derivativeas previously discussed.

[0044] The tubular carbonaceous material derivative of the fourthembodiments exhibits similar desirable and advantageous properties asthe proton conductor materials of the previously discussed embodiments,such as, these materials provide a medium through which protons migrateeasily even under a dry state.

[0045] As previously discussed, the principal reason why the protonconductors of the present invention can exhibit such an excellent protonmigration characteristic is that a large number of functional groups,such as, hydroxyl and —OSO₃H groups, can be introduced to the tubularcarbonaceous material of the tubular carbonaceous material derivatives.

[0046] The tubular carbonaceous material derivative of the fourthembodiment includes a carbon nano-tube (CNT) material, such as, a singlewall carbon nano-tube material (SWCNT), a multi-wall carbon nano-tubematerial (MWCNT), a carbon nano-fiber material (CNF), or other liketubular carbonaceous material.

[0047] The tubular carbonaceous material is characterized in that aratio of an axial length to a diameter of the tubular carbonaceousmaterial is very large, and further the tubular carbonaceous moleculesof this material are entangled in a complicated form or structure thatis inherent to this kind of material. Accordingly, a large number of thefunctional groups can be introduced onto the surfaces of the tubularcarbonaceous molecules of these carbonaceous materials (see FIGS.20-22).

[0048] In particular, the tubular carbonaceous material of the fourthembodiment makes it possible to increase the number of stable protonsites from which the protons can singly migrate without the use ofcarrier molecules, such as, water, and to continuously distribute thestable proton sites over an entire region of the material.

[0049] The fourth method of producing a proton conductor that includes atubular carbonaceous material derivative as discussed can be easilyproduced by preparing a halogenated or non-halogenated tubularcarbonaceous material; then subjecting the material to an acid treatmentor hydrolysis and an acid treatment or a plasma treatment. This materialcan then be easily formed into a film by dispersing the tubularcarbonaceous material derivative within a liquid such as water and thenfiltering the dispersion of the derivative.

[0050] The film thus formed, in which tubular molecules are entangled,has a large strength, a high stability, and a good proton conductivity.When used for a general electrochemical device, the proton conductor isrequired to be configured as an aggregate of the tubular carbonaceousmaterial derivative, and in particular, when used for a fuel cell, theproton conductor is required to be configured as a thin film having ahigh stability, a high density, a large strength, and a good protonconductivity. Accordingly, it is apparent that the film of the tubularcarbonaceous material derivative according to the present invention isparticularly suitable for such an application.

[0051] The film can then be used for an electrochemical device whereinthe proton conductor of the electrochemical device is formed of thefilm. In this way, the film is mounted as the proton conductor betweenthe first and second electrodes of the electrochemical device such thatit is possible to maintain desirable proton conductivity for a longperiod of time without the need of using any external migration medium,such as, moisture so as to enhance proton conductivity.

DESCRIPTION OF THE DRAWINGS

[0052]FIGS. 1A and 1B are views showing a structure of apolyhydroxylated fullerene molecule as examples of molecules of afullerene derivative of the present invention;

[0053]FIGS. 2A, 2B, and 2C illustrate further examples of molecules ofthe fullerene derivative of the present invention, wherein FIGS. 2A-2Cshow a fullerene derivative that includes fullerene molecules whichcontain —OH groups, —OSO₃H groups, and Z groups, respectively;

[0054]FIGS. 3A and 3B illustrate examples of fullerene molecules;

[0055]FIG. 4 shows examples of carbon clusters of a carbon clusterderivative of the third proton conductor of the present invention;

[0056]FIG. 5 shows further examples of carbon clusters that have partialfullerene structures;

[0057]FIG. 6 shows still further examples of carbon clusters that havediamond structures;

[0058]FIG. 7 shows additional examples of carbon clusters which arebonded to each other;

[0059]FIG. 8 is a schematic view of an example of a proton conductor ofthe present invention;

[0060]FIG. 9 is a sectional view showing a fuel cell that employs aproton conductor of the present invention;

[0061]FIGS. 10A and 10B are diagrams depict equivalent circuits of aexperimental pellets in Inventive Example 1 and Comparative Example 1;

[0062]FIG. 11 is a graph showing a result of measuring the compleximpedances of a pellet (a proton conductor containing a fullerenederivative) in Inventive Example 1 and a pellet in Comparative Example1;

[0063]FIG. 12 is a graph showing a temperature dependence on the protonconductivity of the pellet in Inventive Example 1;

[0064]FIG. 13 is a diagram showing results of the generating electricityexperiment using the fullerene derivative in Inventive Example 1.

[0065]FIG. 14 is a graph showing a result of measuring the compleximpedance of a pellet (a proton conductor containing a fullerenederivative and a polymer material) in Inventive Example 4 and a pelletin Comparative Example 2;

[0066]FIG. 15 is a graph showing a temperature dependence on the protonconductivity of the pellet in Inventive Example 4;

[0067]FIG. 16 is a graph showing a TOF-MS spectrum of a carbon powderproduced by an arc discharge process using a carbon electrode;

[0068]FIG. 17 is a sectional view of a hydrogen-air cell that employs aproton conductor of the present invention;

[0069]FIG. 18 is a schematic configuration view of anotherelectrochemical device using the proton conductor of the presentinvention;

[0070]FIG. 19 is a schematic configuration view of a furtherelectrochemical device using a proton conductor of the presentinvention.

[0071]FIG. 20 illustrates a tubular carbonaceous material derivative ofthe present invention;

[0072]FIG. 21 further illustrates a number of tubular carbonaceousmolecules of the tubular carbonaceous material derivative as shown inFIG. 20;

[0073]FIG. 22 illustrates another example of tubular carbonaceousmolecules of a tubular carbonaceous material derivative;

[0074]FIG. 23 is a graph that depicts the measuring a complex impedanceof a film used in Inventive Example 10;

[0075]FIGS. 24A and 24B each illustrate examples of tubular carbonaceousmaterials of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] Hereinafter, embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings.

[0077] A first proton conductor according to a first embodiment of thepresent invention mainly contains a fullerene derivative that includes anumber of functional groups so as to be capable of transferring protonsbetween the functional groups of the fullerene derivative.

[0078] According to this embodiment, the kind of fullerene molecule ormolecules used as a base material for the fullerene derivative to whichfunctional groups capable of transferring protons are introduced is notparticularly limited insofar as the fullerene molecules arecharacterized as a spherical carbon cluster or carbon clusters thatgenerally include the C₃₆, C₆₀ (see FIG. 3A), C₇₀ (see FIG. 3B), C₇₆,C₇₈, C₈₀, C₈₂, and C₈₄ fullerene molecules. It should be noted that amixture of these fullerene molecules or other like fullerene moleculesmay also be used as the base material of the fullerene derivative.

[0079] The fullerene molecule was found in the mass spectrum of a beamof carbon cluster created by laser abrasion of graphite in 1985. (H. W.Kroto, J. R. Heath, S. C. O'Brien, R. F. Curl and R. E. Smalley, Nature,318, 162 (1985)). The method of producing the fullerene molecules by arcdischarge of a carbon electrode was established five years later in1990. Ever since the establishment of the practical production method,the fullerene molecules have become a focus of attention as acarbon-based semiconductor material or the like.

[0080] The present invention has uniquely and advantageously examinedthe proton conductivities of derivatives of these fullerene molecules,and found that a polyhydroxylated fullerene obtained by introducinghydroxyl groups to a number of carbon atoms of a fullerene molecule ormolecules exhibits, even in a dry state, a high proton conductivity in awide temperature range including an ordinary temperature region, thatis, a temperature range from less than the freezing point of water tomore than the boiling point of water (at least −40° C. to 160° C.), andfurther found that the proton conductivity becomes higher whenhydrogensulfate ester groups, namely, —OSO₃H groups, are introduced, inplace of the hydroxyl groups, to the fullerene molecule or molecules.

[0081] To be more specific, the polyhydroxylated fullerene or fullernolis a generic name of a fullerene-based compound that has a structure inwhich a plurality of hydroxyl groups are added to the fullerene moleculeor molecules as shown in FIGS. 1A and 1B. Of course, with respect to thenumber, arrangement, and the like of the hydroxyl groups of thefullerene molecule, some variations can be considered. The firstsynthesis example of the polyhydroxylated fullerene has been reported byChiang, et al. in 1992. (L. Y. Chiang, J. W. Swirczewski, C. S. Hsu, S.K. Chowdhury, S. Cameron and K. Creengan, J. Chem. Soc, Chem. Commun.,1791 (1992)). Since this report, the polyhydroxylated fullerene thatcontains a specific amount or more of the hydroxyl groups has become afocus of attention, particularly, in terms of its water-soluble ability,and has been studied mainly in the biotechnological field.

[0082] In an embodiment, the present invention has newly discovered thata fullerene derivative can be formed from an aggregate of thepolyhydroxylated fullerene molecules, as schematically shown in FIG. 2A,in which the hydroxyl groups of each of these molecules adjacent to eachother (in the figure, ◯ designates the polyhydroxylated fullerenemolecule) act on each other, thereby exhibiting a high protonconductivity (that is, a high transferability of H⁺ between the phenolichydroxyl groups of the polyhydroxylated fullerene molecule or molecules)within the bulk or aggregate of the polyhydroxylated fullerenemolecules.

[0083] As the first proton conductor in this embodiment, the aggregateof fullerene molecules wherein each or a number of the molecules have aplurality of —OSO₃H groups may be used in place of the aggregate ofpolyhydroxylated fullerene molecules as previously discussed. Thefullerene-based compound in which the OH groups are replaced with the—OSO₃H groups as show in FIG. 2B, that is, ahydrogensulfate-esterificated fullerenol (polyhydroxyl hydrogen sulfatedfullerene) was reported by Chiang, et al. in 1994. (L. Y. Chiang, L. Y.Wang, J. W. Swirczewski, S. Soled and S. Cameron, J. Org. Chem. 59, 3960(1994)). The molecules of polyhydroxyl hydrogen sulfated fullerene maycontain only the —OSO₃H groups or contain a number of the —OSO₃H groupsand a number of the hydroxyl groups.

[0084] In the case of preparing the fullerene derivative of the presentinvention, an aggregate of a large number of fullerene derivativemolecules that contain the hydroxyl groups or —OSO₃H groups orcombinations thereof is prepared. Since the protons derived from a largeamount of hydroxyl groups or —OSO₃H groups or combinations thereof thatare originally contained in the molecules directly migrate, the protonconductivity of the bulk or aggregate of these fullerene molecules isself-determined without the need of entrapment of hydrogen resultingfrom steam molecules or protons from an atmosphere and also without theneed of supply of water from an external environment, particularly, theneed of absorption of water or the like from atmospheric air. In otherwords, the proton conductivity of the aggregate of the fullerenemolecules that contain the functional groups is not limited by theenvironmental atmosphere. Further, the fullerene molecules as the basematerial of the fullerene derivative particularly have an electrophilicproperty, which property may allow not only the —OSO₃H groups having ahigh acidity but also the hydroxyl groups to largely promote theionization of hydrogen. This is one of the reasons why the first protonconductor of an embodiment of the present invention exhibits anexcellent proton conductivity.

[0085] According to the first proton conductor of an embodiment of thepresent invention, since a large amount of hydroxyl groups or —OSO₃Hgroups or combinations thereof can be introduced to each or a number ofthe fullerene molecules of the fullerene derivative, the numericaldensity of protons related to conductivity per unit volume of theconductor becomes very large. This is another reason why the firstproton conductor in this embodiment exhibits an effective conductivity.

[0086] Since the fullerene molecule or molecules of the fullerenederivative of the first proton conductor in this embodiment are mostlyor substantially composed of carbon atoms, the fullerene derivative islight in weight, not easily decomposed, and relatively pure, that is,relatively free of contaminants that may negatively impact its desirableproton conductivity properties. In addition, the cost that is requiredto produce the fullerene derivative has been rapidly lowered.Accordingly, the fullerene may be regarded as a desirable carbonaceousmaterial based on resource, environmental, economic or other desirableconsiderations as previously discussed.

[0087] As a result of the present invention, it is further discoveredthat the functional groups, as discussed above, are not limited to thehydroxyl or —OSO₃H functional groups.

[0088] To be more specific, the functional groups can be expressed by achemical formula of —XH where X is an arbitrary atom or atomic grouphaving a bivalent bond, and further the group can be expressed by achemical formula of —OH or —YOH where Y is an arbitrary atom or atomicgroup having a bivalent bond. In particular, the functional groups arepreferably at least one of the —OH and —OSO₃H, and —COOH, —SO₃H and—OPO(OH)₃ functional groups.

[0089] According to this embodiment, electron attractive groups, suchas, nitro groups, carbonyl groups and carboxyl groups, nitrile groups,alkyl halide groups or halogen atoms (fluorine or chlorine atoms) may bepreferably introduced together with the functional groups, to carbonatoms of the fullerene molecule or molecules. FIG. 2C shows a fullerenemolecule to which Z is introduced in addition to —OH, where Z representsat least one of the —NO₂, —CN, —F, —Cl, —COOR, —CHO, —COR, —CF₃, or—SO₃CF₃ (R is an alkyl group) electron attractive groups. With thepresence of the electron attractive groups in addition to the functionalgroups, it is easy for protons to be released from the functional groupsand to be transferred between the functional groups by the electronattractive effect of the electron attractive groups.

[0090] According to this embodiment, the number of the functional groupscan be freely selected insofar as it is less than the number of thecarbon atoms of the fullerene molecule or molecules, and preferably mayinclude 5 functional groups or more. To keep the π electroncharacteristic of the fullerene molecule for achieving the effectiveelectron attractive ability, the number of functional groups is morepreferably half or less than half of the number of carbon atoms of afullerene molecule or molecules.

[0091] To synthesize the above-described fullerene derivative used forthe first proton conductor of an embodiment, as will be described laterwith reference to examples, desired functional groups may be introducedto carbon atoms of each or a number of the fullerene molecules of thefullerene derivative by subjecting a powder of the fullerene moleculesto known treatments, such as, acid treatment and hydrolysis suitably incombination.

[0092] After treatment, the powder of the fullerene derivative thusobtained can be compacted into a desired shape, for example, into apellet. The compacting of the powder can be performed without use of anybinder, which is effective to enhance the proton conductivity and toreduce the weight of the proton conductor, resulting in a moldedmaterial that substantially contains the fullerene derivative.

[0093] The first proton conductor in this embodiment can be suitablyused for various electrochemical devices. For example, the presentinvention can be preferably applied to an electrochemical device havinga basic structure that includes first and second electrodes and a protonconductor held therebetween, wherein the proton conductor is configuredas the first proton conductor in this embodiment.

[0094] To be more specific, the first proton conductor in thisembodiment can be preferably applied to an electrochemical device inwhich at least one of the first and second electrodes is a gaselectrode, or an electrochemical device in which at least one of thefirst and second electrodes is an active electrode.

[0095] Hereinafter, an example in which the first proton conductor inthis embodiment is applied to a fuel cell will be described.

[0096]FIG. 8 is a schematic view showing the proton conductance of thefuel cell in which a proton conducting portion 1 is held between a firstelectrode (for example, hydrogen electrode) 1 and a second electrode(for example, oxygen electrode) 3, wherein protons dissociated ortransferred in the proton conducting portion 1 migrate from the firstelectrode 2 side to the second electrode 3 side along the directionshown by an arrow in FIG. 8.

[0097]FIG. 9 is a schematic view showing one example of the fuel cellusing the first proton conductor in this embodiment. The fuel cell isconfigured such that a negative electrode (fuel electrode or hydrogenelectrode) 2 to or in which a catalyst 2 a is closely overlapped ordispersed and which has a terminal 8 faces to a positive electrode(oxygen electrode) 3 to or in which a catalyst 3 a is closely overlappedor dispersed and which has a terminal 9, and a proton conducting portion1 is held therebetween. Upon use of the fuel cell, hydrogen is suppliedfrom an inlet 12 on the negative electrode 2 side, and is dischargedfrom an outlet 13 (which is sometimes not provided) on the negativeelectrode 2 side. During a period in which fuel (H₂) 14 passes through aflow passage 15, protons are generated. The protons migrate togetherwith protons generated in the proton conducting portion 1, onto thepositive electrode 3 side, and react with oxygen (air) 19, which hasbeen supplied in a flow passage 17 from an inlet 16 and flows toward anoutlet 18, to generate a desired electromotive force.

[0098] According to the fuel cell having the above configuration, sincethe protons generated in the proton conducting portion 1 migrate,together with the protons supplied from the negative electrode 2 side,onto the positive electrode 3 side, the proton conductivity becomeshigher. As a result, it is possible to eliminate the need of anyhumidifier or other water source or other external migration medium andhence to simplify the configuration of the system and reduce the weightof the system.

[0099] A second embodiment of the present invention will be describedbelow. The second embodiment is different from the first embodiment inthat the above-described fullerene derivative is used in combinationwith a polymer material. However, the proton conductor of the secondembodiment essentially has the same proton conductivity features of thefirst embodiment.

[0100] A second proton conductor in this embodiment contains theabove-described derivative and a polymer material.

[0101] The polymer material may be one kind or two kinds or more knownpolymers having a film formation ability. The content of the polymermaterial is generally 20 wt % or less. If the content is more than 20 wt%, the proton conductivity of the fullerene derivative may degrade.

[0102] Since the second proton conductor in this embodiment contains thefullerene derivative, it can exhibit a proton conductivity comparable tothat of the first proton conductor of the first embodiment.

[0103] While the first proton conductor in the first embodimentcontaining only the fullerene derivative is used as a compacted powderas described above, the second proton conductor in this embodimenthaving a film formation ability derived from the polymer material can beused as a flexible proton conductive thin film having a large strengthand a gas impermeable property. In general, the thickness of the protonconductive thin film is 300 μm or less.

[0104] The kind of polymer material is not particularly limited insofaras it does not obstruct the proton conductivity as much as possible (dueto the reaction with the fullerene derivative or the like) and has afilm formation ability, but may be generally selected from polymershaving no electronic conductivity and exhibiting a good stability.Examples of these polymers may include polytetrafluoroethylene,polyvinylidene fluoride, and polyvinyl alcohol. The reason whypolytetrafluoroethylene, polyvinylidene fluoride or polyvinyl alcoholare suitable for the second proton conductor in this embodiment will bedescribed below.

[0105] The reason why polytetrafluoroethylene is suitable for the secondproton conductor is that it has a good film formation ability. Even byadding polytetrafluoroethylene to the fullerene derivative in an amountsmaller than that of another polymer material, it is possible to easilyform a thin film of the second proton conductor having a large strength.The content of polytetrafluoroethylene includes 3 wt % or less,preferably, in a range of 0.5 to 1.5 wt %. By addingpolytetrafluoroethylene to the fullerene derivative in an amount withinthe above range, the thin film of the second proton conductor has athickness that ranges from 1 μm to 100 μm.

[0106] The reason why polyvinylidene fluoride or polyvinyl alcohol aresuitable for the second proton conductor is that it is effective to forma proton conductive thin film having a good gas permeation preventiveability. The content of polyvinylidene fluoride or polyvinyl alcohol mayrange from 5 to 15 wt %. If the content of polyvinylidene fluoride orpolyvinyl alcohol is less than the lower limit of the above range, theremay occur an adverse effect exerted on the film formation.

[0107] The thin film of the second proton conductor in this embodimentmay be obtained by using a known film formation technique, such as,extrusion molding.

[0108] The second proton conductor in this embodiment can be preferablyapplied to the electrochemical device to which the first protonconductor in the first embodiment is applied.

[0109] That is to say, in the electrochemical device to which the firstembodiment is applied, in which the first proton conductor is heldbetween the first and second electrodes, the first proton conductor maybe replaced with the second proton conductor in this embodiment.

[0110]FIG. 17 is a schematic view showing a hydrogen-air cell to whichthe second proton conductor in this embodiment is applied. In thisdevice, a hydrogen electrode 21 faces to an air electrode 22 with aproton conductor 20 formed into a thin film (configured as the secondproton conductor) held therebetween, and the outsides of theseelectrodes 21 and 22 are held between a Teflon plate 24 a and a Teflonplate 24 b having a number of holes 25 and fixed thereto by way of bolts26 a and 26 b and nuts 27 a and 27 b, wherein a hydrogen electrode lead28 a and an air electrode lead 28 b extending from the electrodes 21 and22 are extracted to the outside of the cell.

[0111]FIG. 18 is a schematic view showing an electrochemical device towhich the second proton conductor in this embodiment is applied.Referring to FIG. 18, a proton conductor 34 (configured as the secondproton conductor) is held between a negative electrode 31 having on itsinner surface a negative electrode active material layer 30 and apositive electrode (gas electrode) 33 having on its outer surface a gaspermeation support 32. The negative electrode active material may beconfigured as a hydrogen absorption alloy or a hydrogen absorption alloysupported by a carbon material such as a fullerene. The gas permeationsupport 32 may be configured as a porous carbon paper. The positiveelectrode 33 may be preferably formed by coating a paste of platinumsupported by a powder of carbon. Gaps between the outer ends of thenegative electrode 31 and the outer ends of the positive electrode 33are blocked by gaskets 35. In this electrochemical device, charging canbe performed by making water be present on the positive electrode 33side.

[0112]FIG. 19 is a schematic view showing an electrochemical device towhich the second proton conductor in this embodiment is applied.Referring to FIG. 19, a proton conductor 41 formed into a thin film(configured as the second proton conductor) is held between a negativeelectrode 38 having on its inner surface a negative electrode activematerial layer 37 and a positive electrode 40 having on its innersurface a positive electrode active material layer 39. The positiveelectrode active material is typically configured as a material mainlycontaining nickel hydroxide. Even in this electrochemical device, gapsbetween the outer ends of the negative electrode 38 and the outer endsof the positive electrode 40 are blocked with gaskets 42.

[0113] Each of the above-described electrochemical devices using thesecond proton conductor in this embodiment can exhibit a good protonconductive effect on the basis of the same mechanism as that of theelectromechanical device using the first proton conductor in the firstembodiment. Further, since the second proton conductor containing thefullerene derivative in combination with the polymer material having afilm formation ability, it can be formed into a thin film having a largestrength and a small gas permeability, and therefore, it can exhibit agood proton conductivity.

[0114] A third embodiment of the present invention will be describedbelow. The third embodiment is different from the first and secondembodiments in that the proton conductor mainly contains a carboncluster derivative or derivatives, but is the same or similar to thefirst and second embodiments in other ways, such as, the basic functionof the proton conduction mechanism.

[0115] A third proton conductor in this embodiment mainly contains acarbon cluster derivative in which the functional groups are introducedto a number of carbon atoms of each of the clusters or carbon clusterswhich are used as a base material for the carbon cluster derivative.

[0116] The reason why the cluster(s) or carbon cluster(s) are used asthe base material in this embodiment is that a large number offunctional groups can be introduced to each cluster or carbon clustervia their respective carbon atoms. By introducing a large number offunctional groups onto the cluster or carbon cluster, a desirable protonconductivity is achieved due to the fact that the introduction of alarge number of functional groups significantly increases the acidity ofthe solid-state proton conductor. In addition, the increased acidity haslittle, if any, effect on the integrity of the chemical structure of thecluster or carbon cluster because atoms of the carbon cluster or clusterare so closely bonded to one another. With this closely-bonded chemicalstructure, the carbon cluster or cluster are superior in durability toother known carbonaceous or carbon-based materials, thereby resulting ina desirable film structure for the proton conductor.

[0117] The third proton conductor in this embodiment having the aboveconfiguration can exhibit, even in a dry state, a high protonconductivity similar to that of each of the first and second protonconductors in the first and second embodiments.

[0118] As defined above, the “carbon cluster” means an aggregate of upto several hundred carbon atoms that are closely bonded togetherirrespective of the carbon to carbon molecular-type bonding that existsbetween the carbon atoms. It should be noted that the carbon cluster,that is, an aggregate of that substantially contains carbon atoms is notnecessarily entirely composed of carbon atoms. Various types of carbonclusters or aggregates of carbon atoms are shown in FIGS. 4 to 7. Inthese figures, the functional groups, for example, hydroxyl groups, arenot shown.

[0119]FIG. 4 shows carbon clusters having spherical structures, spheroidstructures, and planar structures similar thereto. FIG. 5 shows carbonclusters that have a partially open spherical structure which ischaracterized by an open end or ends. During production of the fullerenemolecules by arc discharge, a large number of carbon clusters having aspherical structure with open ends are generated as sub-products. FIG. 6shows carbon clusters each having a diamond structure, in which most ofthe carbon atoms of the carbon cluster are in the SP³ bonding.

[0120] A carbon cluster material in which most of the carbon atoms arein the SP² bonding has a planar structure of graphite or has all or partof a fullerene or nano-tube structure. While it is not a problem thatthe carbon cluster material having a planar structure or graphite isused as the base or other component of the proton conductor, the protonconductivity should be larger than an electronic conductivity in totalin the proton conductor.

[0121] On the contrary, a fullerene or nano-tube structure that has theSP² bonding often has no electronic conductivity because it alsopartially contains an element that exhibits the desirable SP³ bonding.While some nano-tube structure has an electronic conductivity, theelectronic conductivity can be vanished or lessened by introducing theabove-mentioned functional groups to the nano-tube structure. Therefore,these carbon materials are desirable as the base of a proton conductor.

[0122]FIG. 7 shows carbon clusters which are bonded to each other. FIG.7, thus, represents examples of carbon clusters that can be utilized tomake the carbon cluster derivative of the proton conductor in anembodiment of the third proton conductor of the present invention.

[0123] To form the third proton conductor in this embodiment, it isrequired to introduce functional groups to the clusters or carbonclusters. Further, it may be desirable to further introduce electronicattractive groups to each of the clusters or carbon cluster. Thefunctional groups may be introduced to each carbon cluster in accordancewith the following production method.

[0124] According to the production method of the present invention, acarbon cluster derivative can be easily obtained by producing carbonclusters composed of carbon powder by arc discharge of a carbon-basedelectrode, and suitably subjecting the carbon clusters to acidtreatment, typically using sulfuric acid and hydrolysis, and alsosubjected to sulfonation or phosphatation so as to introduce the sulfurand phosphorus-based functional groups, respectively.

[0125] The carbon cluster derivative can be compacted into a suitableshape, for example, into a pellet. According to the third protonconductor in this embodiment, the length of the major axis of each ofthe carbon clusters as the base of the carbon cluster derivatives of theproton conductors may be 100 nm or less, preferably, 100 Å or less, andthe number of functional groups to be introduced therein may bepreferably 2 or more.

[0126] The carbon cluster used for the third proton conductor may be ofa cage structure at least part of which has open ends. The carbonclusters having such a case structure has a reactivity similar to thatof a fullerene and also has a higher reactivity at its defect portions,that is, its open end portion or portions. Accordingly, the use ofcarbon clusters each having such a defect structure, that is, open endor ends, as the base of the third proton conductor can promote theintroduction of functional groups by acid treatment or the like, thatis, increase the introduction efficiency of the functional groups,thereby enhancing proton conductivity of the third proton conductor.Further, it is possible to synthesize a larger amount of carbon clustersas compared with fullerene molecules, and hence to produce the carbonclusters at a very low cost.

[0127] The kinds of functional groups and the electron attractive groupsto be introduced to each of the carbon clusters as the base of the thirdproton conductor in this embodiment may be the same as those describedabove.

[0128] The third proton conductor in this embodiment can be suitablyapplied to various kinds of electrochemical devices, such as, a fuelcell. In this case, the configuration of the electrochemical device maybe basically the same as that of the electromechanical device to whichthe first or second proton conductor in the first or second embodimentis applied except that the first or second proton conductor is replacedwith the third proton conductor. Since the third proton conductor inthis embodiment can also exhibit a good proton conductivity even in adry state, it is possible to eliminate the need of providing anyhumidifier or other like instrument that produces an external migration,such as, water or steam, and hence to simplify the system configurationand reduce the weight of the system.

[0129] A fourth embodiment of the present invention will be describedbelow in which the proton conductor includes a tubular carbonaceousmaterial derivative. The tubular carbonaceous material derivativeincludes a tubular carbonaceous material as its base material. Thetubular carbonaceous material includes a CNT material that is composedof nano-tube molecules that each have a diameter of about severalnanometers or less, typically, in a range of 1 to 2 nanometers. Inaddition to the CNT material, the tubular carbonaceous material includesa CNF material that is composed of nano-fiber molecules which each havea diameter of several nanometers or more which may reach up to 1 mm.Further, it is known that the CNT material includes a single-wall carbonnano-tube (SWCNT) material that is composed of nano-tube molecules eachbeing formed by a single layer or a multi-wall carbon nano-tube (MWCNT)that is composed of nano-tube molecules that are each formed of two ormore layers which are concentrically overlapped.

[0130] The configurations of the SWCNT and the MWCNT molecules arerespectively shown in FIGS. 24A and 24B. In addition, the description ofthe CNT, the SWCNT and MWCNT materials are illustrative only wherein itis understood that the present invention is not limited to the same.

[0131] According to the fourth embodiment of the present invention, thefunctional groups that are introduced to the tubular carbonaceousmaterials in order to form the tubular carbonaceous material derivativesinclude the same functional groups as previously discussed in regards tothe other embodiment of the present invention. As illustrated, FIG. 20shows an example of a tubular carbonaceous material derivative thatcontains the hydroxyl functional groups. In addition, FIG. 21illustrates a number of the tubular carbonaceous molecules or tubularmolecules of the tubular carbonaceous material derivative as shown inFIG. 20. As well, FIG. 22 illustrates the tubular molecules of anothertubular carbonaceous material derivative that includes the —OSO₃Hfunctional groups. Such a tubular carbonaceous material derivative isproduced by preparing a halogenated tubular carbonaceous material andsubjecting the halogenated material to acid treatment by using sulfuricor nitric acid in order to introduce the —OSO₃H functional groups to thetubular carbonaceous material so as to form its derivative. In addition,a hydrolysis technique may be used to introduce hydroxyl groups insteadof the —OSO₃H functional groups. If hydrolysis is used, an acidtreatment may follow in order to substitute the hydroxyl groups fordifferent functional groups, such as, the —OSO₃H functional groups.

[0132] If a non-halogenated tubular carbonaceous material is used as abase or raw material so as to form the tubular carbonaceous materialderivative, this material may be subjected to acid treatment by usingsulfuric or nitric acid as previously discussed. With regards to thehalogenated tubular carbonaceous material, fluorine is preferably used.

[0133] The tubular carbonaceous material derivative can be produced notonly by the above described wet method but also by the following drymethod that utilizes plasma. In this method, a non-halogenated tubularcarbonaceous material is subjected to plasma treatment in an oxygen gasand then subjected to further plasma treatment under a hydrogen gas inorder to introduce the functional groups, typically, hydroxyl groups tothe tubular molecules of the tubular carbonaceous material.

[0134] The invention has examined the proton conductivities of thesetubular carbonaceous material derivatives and found that these materialsprovided a high proton conductivity under a varying temperature rangethat includes the ordinary temperature region, that is, a temperatureranging from less than the freezing point of water to more than theboiling point of water (at least −40° C. to 160° C. The presentinvention has further discovered that the proton conductivity is higherfor tubular carbonaceous material derivatives that include the hydrogensulfate as their groups in place of the hydroxyl groups.

[0135] In particular, the polyhydroxylated SWCNT material is a genericname of a derivative that has a structure in which a plurality ofhydroxyl groups are added to a number of tubular molecules so as to formthe SWCNT material as illustrated in FIG. 20. Of course, with respect tothe number, arrangement and the like of the hydroxyl groups, somevariations are considered to be within the scope of the presentinvention.

[0136] The present invention has newly discovered that an aggregate ofpolyhydroxylated tubular molecules, namely, a polyhydroxylated SWCNTmaterial, as illustrated in FIGS. 20 & 21, in which the hydroxyl groupsof the tubular molecules adjacent to each other act on each other toexhibit a high proton conductivity, that is, a high transfer ormigration ability of H⁺ or protons from the phenolic hydroxy groups thatare contained in each of the tubular molecules of the polyhydroxylatedSWCNT material or bulk material.

[0137] The proton conductor of the fourth embodiment includes the sametype and arrangement of functional groups as the proton conductor of theother embodiments. For example, the proton conductor may includefunctional groups such as hydroxyl groups, OSO₃H groups, andcombinations of these groups thereof.

[0138] The proton conductivity of the tubular carbonaceous materialderivative that includes an aggregate of the tubular molecules having anumber of functional groups, like the proton conductivity of the otherproton conductor embodiments, is not limited by the environmentalsurroundings. In this way, an additional source of protons frommigrating mediums, such as, water is not necessary in order to realizethe desirable effects of the present invention. Similar to the otherembodiments, the reason why the tubular carbonaceous material derivativecan exhibit such a desirable proton conductivity effect is that a largeamount of the functional groups can be introduced to a number of thetubular molecules of the tubular carbonaceous material so that theproton density which corresponds to the conductivity per unit volume ofthe conductor is very large in size.

[0139] In addition, the tubular carbonaceous material derivative ismostly composed of carbon atoms of each of the tubular molecules andtherefore is light in weight and does not decompose as readily norcontain any contaminants. Moreover, the tubular carbonaceous materialthat is used for a base material for producing the derivative thereofcan be produced by catalytic thermal decomposition of hydrocarbons at alow cost. As a result, the tubular carbonaceous material is regarded asa material that is desirable for reasons of resource, environment andeconomy. (Carbon Vol. 36, No. 11, pp. 1603-1612, 1998, 1978, EiseierScience Ltd., Printed in Great Britain).

[0140] As previously discussed, the tubular carbonaceous materialderivative includes a number of functional groups that provide thedesirable proton conductivity effect. The functional groups of thisderivative are similar in number and type and arrangement as thefunctional groups of the other embodiments as previously discussed. Inaddition, the tubular carbonaceous material derivatives can include anelectron attractive group as previously discussed in the otherembodiments of the proton conductor. With the presence of the electronattractive groups, the proton can more easily migrate or transferbetween functional groups of the derivative due to the electronattractive effect of the electron attractive groups.

[0141] With respect to the number of functional groups of the tubularcarbonaceous material derivative, the number is limited to the extentthat it is less than the number of carbon atoms of the tubularcarbonaceous material derivative. In addition, the number of functionalgroups may be limited to the extent that is necessary to cancel theelectronic conductivity. For example, this number is preferably one ormore per ten carbon atoms for a CNT material.

[0142] In addition to the functional groups and electron attractivegroups, the proton conductor that mainly contains the tubularcarbonaceous material derivatives may further contain anothercarbonaceous material derivative, such as, a fullerene derivative thatincludes a number of functional groups as previously discussed. Examplesof fullerene molecules that make-up the fullerene derivative have beenpreviously discussed and are further illustrated in FIGS. 3A and 3B.

[0143] By combining the tubular carbonaceous material with the fullerenematerial, the advantageous and desirable properties can be combined tomeet the needs for a variety of different applications of thesematerials. The tubular carbonaceous material forms a strong and stablefilm that is suitable for an electrochemical device due to the fact thatits axial length is much longer than its diameter and that the tubularmolecules are entangled in a complicated form. This structure isstronger than an aggregate of a fullerene derivative that includesspherical fullerene molecules. However, the fullerene derivative moreeasily reacts with the functional groups and thereby a higher protonconductivity can be obtained on these materials versus the tubularcarbonaceous materials.

[0144] According to the present invention, tubular carbonaceous materialderivatives may be desirably formed as a film to be used for anelectrochemical device such as a fuel cell. These materials can beformed as a film by a known extrusion molding technique and morepreferably by dispersing the tubular carbonaceous material derivative ina liquid and filtering the dispersion. A solvent such as water isgenerally used as the liquid. However, the liquid is not particularlylimited insofar as the derivative can be dispersed in the liquid.

[0145] By filtering the dispersion, the tubular carbonaceous materialderivative is deposited in a film shape on the filter. The film does notcontain any binder and is composed of only the tubular carbonaceousmaterial derivative wherein the tubular molecules are entangled incomplicated form. Such a film has a very high strength and can be easilypeeled from the filter. In this case, if the fullerene derivative isdispersed in combination with the tubular carbonaceous materialderivative in the liquid, it is possible to easily form a composite filmwhich is composed of a combination of these materials which again doesnot contain any binder.

[0146] As previously discussed, the proton conductor that mainlyincludes a tubular carbonaceous material derivative is preferably usedfor a fuel cell. The fuel cell application of this material is similarto the application of the other previously discussed materials. Thepresent invention will be more clearly understood with reference to thefollowing examples:

[0147] I. Fullerene Derivative

[0148] <(Synthesis of Polyhydroxylated Fullerene>

[0149] The synthesis of polyhydroxylated fullerene was performed withreference to L. Y. Chaing, L. Y. Wang, J. W. Swircczewski, S. Soled andS. Cameron, J. Org. Chem. 59, 3960 (1994). First, 2 g of a powder of amixture of C₆₀ and C₇₀. containing about 15% of C₇₀ was put in 30 ml offuming sulfuric acid, and was stirred for three days while being kept ina nitrogen atmosphere at 60° C. The reactant was put little by little indiethyl ether anhydride cooled in an ice bath, and the deposit wasfractionated by centrifugal separation, cleansed twice by diethyl etherand twice by a mixture of diethyl ether and acetonitrile at a mixingratio of 2:1, and dried under a reduced pressure at 40° C. The depositthus cleaned and dried was put into 60 ml of ion exchange water, andstirred for 10 hours at 85° C. while being subjected to bubbling usingnitrogen. The reactant was subjected to centrifugal separation, toseparate a deposit, and the deposit was cleaned several times by purewater, repeatedly subjected to centrifugal separation, and dried under areduced pressure at 40° C. A brown powder thus obtained was subjected toFT-IR measurement. As a result, the IR spectrum of the brown powdernearly conformed to that of C₆₀(OH)₁₂ shown in the above document, andtherefore, it was confirmed that the powder was the polyhydroxylatedfullerene as the target material.

[0150] <Production of Pellet of Aggregate of Polyhydroxylated Fullerene>

[0151] Next, 90 mg of the powder of the polyhydroxylated fullerene waspressed in one direction at a pressure of about 5 tons/cm² into acircular pellet having a diameter of 15 mm. Since the compactivity ofthe powder of polyhydroxylated fullerene was excellent although thepowder contained no binder resin, the powder of the polyhydroxylatedfullerene could be easily formed into a pellet having a thickness ofabout 300 μm. Such a pellet is taken as a pellet in Inventive Example 1.

[0152] <Synthesis (Part 1) of Poly-Hydrogen-Sulfated Fullerene>

[0153] The synthesis of a poly-hydrogen-sulfated fullerene or hydrogensulfated fullerene was performed with reference to the above-describeddocument. First. 1 g of a powder of a polyhydroxylated fullerene was putin 60 ml of fuming sulfuric acid, and was stirred for three days whilebeing kept in a nitrogen atmosphere at ordinary temperature. Thereactant was put little by little in diethyl ether anhydride, cooled inan ice bath, and the deposit was fractionated by centrifugal separation,cleansed three-times by diethyl ether and twice by a mixture of diethylether and acetonitrile at a mixing ration of 2:1, and dried under areduced pressure at 40° C. A powder thus obtained was subjected to FT-IRmeasurement. As a result, the IR spectrum of the powder nearly conformedto that of a poly-hydrogen-sulfated fullerene in which the hydroxylgroups were entirely replaced with hydrogen sulfated groups, i.e. —OSO₃Hgroups, shown in the document, and therefore, it confirmed that thepowder was the poly-hydrogen-sulfated fullerene as the target material.The above-described reaction is represented, for example, concerningC₆₀(OH)_(y) as follows (here and hereinafter):

[0154] <(Production (Part 1) of Pellet of Aggregate ofPoly-Hydrogen-Sulfated Fullerene>

[0155] Next, 70 mg of the powder of poly-hydrogen-sulfated fullerene waspressed in one direction at a pressure of about 5 tons/cm² into acircular pellet having a diameter of 15 mm. Since the compactivity ofthe powder of poly-hydrogen-sulfated fullerene was excellent althoughthe powder contained no binder resin, the powder ofpoly-hydrogen-sulfated fullerene could be easily formed into a pellethaving a thickness of about 300 μm. Such a pellet is taken as a pelletin Inventive Example 2.

[0156] <Synthesis (Part 2) of Partially Hydrogensulfate-EsterificatedPolyfullerene Hydride (Polyhydroxyl Hydrogen Sulfated Fullerene)>

[0157] First, 2 g of powder of a mixture of C₆₀ and C₇₀ containing about15% of C₇₀ was put in 30 ml of fuming sulfuric acid, and was stirred forthree days while being kept in a nitrogen atmosphere at 60° C. Thereactant was put little by little in diethyl ether cooled in an icebath. It should be noted that diethyl ether not subjected to dehydrationis used. The deposit thus obtained was fractionated by centrifugalseparation, cleaned three times by diethyl ether and twice by a mixtureof diethyl ether and acetonitrile at a mixing ratio of 2:1, and driedunder a reduced pressure at 40° C. A powder thus obtained was subjectedto FT-IR measurement. As a result, the IR spectrum of the powder nearlyconformed to that of a fullerene derivative containing both of thehydroxyl and OSO₃H groups shown in the document, and therefore, it wasconfirmed that the powder was the polyhydroxyl hydrogen sulfatedfullerene as the target material. The above-described reactions arerepresented, for example, concerning C₆₀ as follows (here andhereinafter):

[0158] <(Production (Part 2) Pellet of Aggregate of PolyhydroxylHydrogen Sulfate Fullerene>

[0159] Next, 80 mg of the powder of a polyhydroxyl hydrogen sulfatedfullerene was pressed in one direction at a pressure of about 5 tons/cm²into a circular pellet having a diameter of 15 mm. Since thecompactivity of the powder of polyhydroxyl hydrogen sulfated fullerenewas excellent although the powder contained no binder resin, the powderof the polyhydroxyl hydrogen sulfated fullerene could be easily formedinto a pellet having a thickness of about 300 μm. Such a pellet is takenas a pellet in Inventive Example 3.

[0160] For comparison, 90 mg of a powder of the fullerene molecules usedas a the raw material for synthesis in the above examples was pressed inone direction at a pressure of about 5 tons/cm² into a circular pellethaving a diameter of 15 mm. Since the compactivity of the powder of thefullerene molecules was relatively excellent although the powdercontained no binder resin, the powder of the fullerene molecules couldbe relatively easily formed into a pellet having thickness of about 300μm. Such a pellet is taken as a pellet in Comparative Example 1.

[0161] <Measurement of Proton Conductivities of Pellets of

[0162] Inventive Examples and Comparative Example>

[0163] To measure a proton conductivity of each of the pellets ofInventive Example 1-3 and Comparative Example 1, both sides of thepellet were held between aluminum plates each having the same diameteras that of the pellet, that is, 15 mm, and AC voltages (amplitude: 0.1V) at frequencies ranging from 7 MHz to 0.01 Hz are applied to thepellet, to measure a complex impedance at each frequency. Themeasurement was performed under a dry atmosphere.

[0164] With respect to the above impedance measurement, a protonconducting portion 1 of a proton conductor composed of the above pelletelectrically constitutes an equivalent circuit shown in FIG. 10A, inwhich capacitances 6 and 6′ are formed between first and secondelectrodes 2 and 3 with the proton conducting portion 1 expressed by aparallel circuit of a resistance 4 and a capacitance 5 heldtherebetween. In addition, the capacitance 5 designates a delay effect(phase delay at a high frequency) upon migration of protons, and theresistance 4 designates a parameter of difficulty of migration ofprotons.

[0165] The measured impedance Z is expressed by an equationZ=Re(Z)+i·Im(Z). The frequency dependency on the proton conductingportion expressed by the above equivalent circuit was examined.

[0166] In addition, FIG. 10B shows an equivalent circuit of a protonconductor (Comparative Example to be described later) using the typicalfullerene molecules without functional groups.

[0167]FIG. 11 shows results of measuring the impedances of the pelletsof Inventive Example 1 and Comparative Example 1.

[0168] Referring to FIG. 11, for Comparative Example 1, the frequencycharacteristics of the complex impedance is nearly the same as thebehavior of a single capacitor, and the conductance of charged particles(electrons, ions and the like) of the aggregate of the fullerenemolecules is not observed at all; while, for Inventive example 1, theimpedance in a high frequency region depicts a flattened but very smoothsingle semi-circular arc, which shows the conductance of some chargedparticles in the pellet, and the imaginary number portion of theimpedance is rapidly raised in a low frequency region, which shows theoccurrence of blocking of charged particles between the aluminumelectrode and the pellet as gradually nearing the DC voltage. Withrespect to the blocking of the charged particles between the aluminumelectrode and the pellet in Inventive Example 1, the charged particleson the aluminum electrode side are electrons, and accordingly, it isapparent that the charged particles in the pellets are not electrons orholes but ions, more specifically, protons in consideration of theconfiguration of the fullerene derivative.

[0169] The conductivity of the above-described charged particles can becalculated on the basis of an intercept of the circular-arc on the highfrequency side with the X-axis. For the pellet of Inventive Example 1,the conductivity of the charged particles become about 5×10⁻⁶ S/cm. Thepellets of Inventive Examples 2 and 3 were subjected to the samemeasurement as described above. As a result, the whole shape of thefrequency characteristics of the impedance in each of the InventiveExamples 2 and 3 is similar to that in Inventive example 1; however, asshown in Table 1, the conductivity of charged particles in each ofInventive Examples 2 and 3, obtained on the basis of an intercept of acircular-arc portion with the X-axis, is different than in InventiveExample 1. TABLE 1 Conductivities of Pellets of Proton Conductors inInventive Examples 1, 2 and 3 (at 25° C.) Kind of Pellets Conductivity(S/cm) Inventive Example 1 5 × 10⁻⁶ Inventive Example 2 9 × 10⁻⁴Inventive Example 3 2 × 10⁻⁵

[0170] As shown in Table 1, the conductivity of the pellet of thefullerene derivative containing the —OSO₃H groups cause ionization ofhydrogen easier than the hydroxyl groups. The results of Table 1 alsoshow that the aggregate of the fullerene derivative containing thehydroxyl groups and OSO₃H groups can exhibit, in a dry atmosphere, agood proton conductivity at ordinary temperature.

[0171] Next, the complex impedance of the pellet produced in InventiveExample 1 was measured in a temperature range from 160° C. to −40° C.,and the conductivity of the pellet was calculated on the basis of acircular-arc portion on the high frequency side of the complex impedancecurve of the pellet measured at each temperature to examine thetemperature dependency on the conductivity. As the results shown in FIG.12 (the Arrhenius plot), it is apparent that the conductivity changed ina straight-line or linear fashion with respect to a change intemperature within the measured temperature range of 160° C. to −40° C.In other words, data of FIG. 12 shows that a single ion conductionmechanism can occur at least within the temperature range of 160° C. to−40° C. The proton conductor mainly containing the fullerene derivativeaccording to the present invention, therefore, can exhibit a good protonconductivity in a wide temperature range from −40° C. to 160° C. thatincludes ordinary temperatures.

[0172] <Forming a Film Including Polyhydroxylated Fullerene of Example 1and Generating Electricity Experiment Using the Film>

[0173] 0.5 g of the powder of the polyhydroxylated fullerene was mixedwith 1 g of tetrahydrofurane (THF), and the mixture wasultrasonic-vibrated for 10 minutes, resulting in the completedissolution of the polyhydroxylated fullerene in THF. After fabricatinga carbon electrode, a film of the polyhydroxylated fullerene was formedby the steps of: masking the surface of the electrode by a plastic maskhaving a rectangular opening, dripping the above-described solution inthe opening, spreading the solution in the opening, drying in a roomtemperature in order to vaporize THF, and removing the mask. The sameamount of electrode described above, with its downward surface having acatalyst, was laid on the film. The upper electrode was pressed by about5 tons/cm² to complete a composite. This composite was incorporated in afuel cell as shown in FIG. 9. A generating electricity experiment wasperformed by supplying hydrogen gas to one electrode and air to anotherelectrode in the fuel cell.

[0174] The experimental result is shown in FIG. 13. The open circuitvoltage was about 1.2V, and the characteristic of the closed circuitvoltage was also excellent against the current value for the fuel cell.

[0175] II. Fullerene Derivative and Polymer Material

[0176] <Production (Part A) of Pellet of Polyhydroxylated Fullerene andPolymer Material>

[0177] First, 70 mg of the powder of the fullerene derivative obtainedby the above-described synthesis was mixed with 10 mg of a powder ofpolyvinylidene fluoride, followed by addition of 0.5 ml ofdimethylformamide thereto, and the powders thus mixed were stirred inthe solvent. The mixture was poured in a circular mold having a diameterof 15 mm, and the solvent was evaporated under a reduced pressure. Themixture from which the solvent was evaporated was then pressed into apellet having a diameter of 15 mm and a diameter of about 300 μm. Such apellet is taken as a pellet 1A of Inventive Example 4.

[0178] <Production (Part B) of Pellet of Polyhydroxylated Fullerene andPolymer Material>

[0179] Similarly, 70 mg of the powder of the fullerene derivative wasmixed with a dispersion containing 60% of a fine powder ofpolytetrafluoroethylene (PTFE) in such a manner that the content of PTFEbecame 1 wt % on the basis of the total amount, and kneaded. The mixturethus kneaded was molded into a pellet having a diameter of 15 mm and athickness of about 300 μm. Such a pellet is taken as a pellet 1B ofInventive Example 4.

[0180] <Synthesis (Part 1) of Poly-Hydrogen-Sulfated Fullerene>

[0181] The synthesis of a poly-hydrogen-sulfated fullerene was performedwith reference to the above-described document. First, 1 g of the powderof a polyhydroxylated fullerene was put in 60 ml of fuming sulfuricacid, and was stirred for three days while kept in a nitrogen atmosphereat ordinary temperature. The reactant was put little by little indiethyl ether anhydride cooled in an ice bath, and the deposit wasfractionated by centrifugal separation, cleaned three times by diethylether and twice by a mixture of diethyl ether and acetonitrile at amixing ratio of 2:1, and dried under a reduced pressure at 40° C. Apowder thus obtained was subjected to FT-IR measurement. As a result,the IR spectrum of the powder nearly conformed to that of a fullerenederivative in which the hydroxyl groups were all hydrogen sulfate groupsshown in the document, and therefore, it was confirmed that the powderwas the poly-hydrogen-sulfated fullerene as the target material.

[0182] <Production (Part 1A) of Pellet of Hydrogen Sulfated

[0183] Fullerene and Polymer Material>

[0184] First, 70 mg of the powder of the poly-hydrogen-sulfatedfullerene derivative was mixed with 10 mg of a powder of polyvinylidenefluoride, followed by addition of 0.5 ml of dimethylformamide thereto,and the powders thus mixed were stirred in the solvent. The mixture waspoured in a circular mold having a diameter of 15 mm, and the solventwas evaporated under a reduced pressure. The mixture from which thesolvent was evaporated was then pressed into a pellet having a diameterof 15 mm and a thickness of about 300 μm. Such a pellet is taken as apellet of 2A of Inventive Example 5.

[0185] <Production (Part 1B) of Pellet of Hydrogen Sulfated

[0186] Fullerene and Polymer Material>

[0187] Similarly, 70 mg of the powder of the poly-hydrogen-sulfatedfullerene was mixed with a dispersion containing 60% of a fine powder ofpolytetrafluoroethylene (PTFE) in such a manner that the content of PTFEbecame 1 wt % on the basis of the total amount, and kneaded. The mixturethus kneaded was molded into a pellet having a diameter of 15 mm and athickness of about 300 μm. Such a pellet is taken as a pellet of 2B ofInventive Example 5.

[0188] <Synthesis (Part 2) of Polyhydroxyl Hydrogen Sulfated Fullerene>

[0189] First, 2 g of a powder of a mixture of C₆₀ and C₇₀ containingabout 15% of C₇₀ was put in 30 ml of fuming sulfuric acid, and wasstirred for three days while being kept in a nitrogen atmosphere at 60°C. The reactant was put little by little in diethyl ether cooled in anice bath. It should be noted that diethyl ether not subjected todehydration is used. The deposit thus obtained was fractionated bycentrifugal separation, cleaned three times by diethyl ether and twiceby a mixture of diethyl ether and acetonitrile at a mixing ratio of 2:1,and dried under a reduced pressure at 40° C. A powder thus obtained wassubjected to FT-IR measurement. As a result, the IR spectrum of thepowder nearly conformed to that of a fullerene derivative containing thehydroxyl groups and OSO₃H groups shown in the document, and therefore,it was confirmed that the powder was the polyhydroxyl hydrogen sulfatedfullerene as the target material.

[0190] <Production (Part 2A) of Pellet of Polyhydroxyl Hydrogen Sulfated

[0191] Fullerene and Polymer Material>

[0192] First, 70 mg of a powder of the polyhydroxyl hydrogen sulfatedfullerene derivative was mixed with 10 mg of a powder of polyvinylidenefluoride, followed by addition of 0.5 ml of dimethylformamide thereto,and the powders thus mixed were stirred in the solvent. The mixture waspoured in a circular mold having a diameter of 15 mm, and the solventwas evaporated under a reduced pressure. The mixture from which thesolvent was evaporated was then pressed into a pellet having a diameterof 15 mm and a thickness of about 300 μm. Such a pellet is taken as apellet of 3A of Inventive Example 6.

[0193] <Production (Part 2B) of Pellet of Polyhydroxylated HydrogenSulfated

[0194] Fullerene and Polymer Material>

[0195] Similarly, 70 mg of the powder of the polyhydroxylated hydrogensulfated fullerene was mixed with a dispersion containing 60% of a finepowder of polytetrafluoroethylene (PTFE) in such a manner that thecontent of PTFE became 1 wt % on the basis of the total amount, andkneaded. The mixture thus kneaded was molded into a pellet having adiameter of 15 mm and a thickness of about 300 μm. Such a pellet istaken as a pellet of 3B of Inventive Example 6.

[0196] <Production (Part A) of Pellet of Fullerene>

[0197] For comparison, 90 mg of a powder of the fullerene molecules usedas the raw material for the synthesis in the above examples was mixedwith 10 mg of a powder of polyvinylidene fluoride, followed by additionof 0.5 ml of dimethylformamide thereto, and the powders thus mixed werestirred in the solvent. The mixture was poured in a circular mold havinga diameter of 15 mm, and the solvent was evaporated under a reducedpressure. The mixture from which the solvent was evaporated was thenpressed into a pellet having a diameter of 15 mm and a thickness ofabout 300 μm. Such a pellet is taken as a pellet of Comparative Example2.

[0198] <Production (Part B) of Pellet of Fullerene>

[0199] For comparison, 70 mg of the powder of the fullerene moleculesused as the raw material for synthesis in the above examples was mixedwith a dispersion containing 60% of a fine powder ofpolytetrafluoroethylene (PTFE) in such a manner that the content of PTFEbecame 1 wt % on the basis of the total amount, and kneaded. The mixturethus kneaded was molded into a pellet having a diameter of 15 mm and athickness of about 300 μm. Such a pellet is taken as a pellet ofComparative Example 3.

[0200] <Measurement of Proton Conductivities of Pellets of Inventive

[0201] Examples and Comparative Example>

[0202] To measure a proton conductivity of each of the pellets ofInventive Example 4-6 and Comparative Example 2, both sides of thepellet were held between aluminum plates each having the same diameteras that of the pellet, that is, 15 mm, and AC voltages (amplitude: 0.1V) at frequencies ranging from 7 MHz to 0.01 Hz are applied to thepellet, to measure a complex impedance at each frequency. Themeasurement was performed under a dry atmosphere.

[0203] With respect to the above impedance measurement, a protonconducting portion 1 of a proton conductor composed of the above pelletelectrically constitutes an equivalent circuit shown in FIG. 10A, inwhich capacitances 6 and 6′ are formed between first and secondelectrodes 2 and 3 with the proton conducting portion 1 expressed by aparallel circuit of a resistance 4 and a capacitance 5 heldtherebetween. In addition, the capacitance 5 designates a delay effect(phase delay at a high frequency) upon migration of protons, and theresistance 4 designates a parameter of difficulty of migration ofprotons. The measured impedance Z is expressed by an equation ofZ=Re(Z)+i·Im(Z). The frequency dependency on the proton conductingportion expressed by the above equivalent circuit was examined. Inaddition, FIG. 10B shows an equivalent circuit of a proton conductor(Comparative Example to be described later) using the typical fullerenemolecules that contain no functional groups capable of dissociating ortransferring protons.

[0204]FIG. 14 shows results of measuring the impedances of the pellet 1Aof Inventive Example 4 and the pellet of Comparative Example 2.

[0205] Referring to FIG. 14, for the pellet of Comparative Example 2,the frequency characteristics of the complex impedance is nearly thesame as the behavior of a single capacitor, and the conductance ofcharged particles (electrons, ions and the like) of the aggregate of thefullerene molecules is not observed at all; while, for the pellet 1A ofInventive Example 4, the impedance in a high frequency region depicts aflattened but very smooth single semi-circular arc, which shows theconductance of some charged particles in the pellet, and the imaginarynumber portion of the impedance is rapidly raised in a low frequencyregion, which shows the occurrence of blocking of charged particlesbetween the aluminum electrode and the pellet as gradually nearing theDC voltage. With respect to the blocking of the charged particlesbetween the aluminum electrode and the pellet 1A of Inventive Example 4,the charged particles on the aluminum electrode side are electrons, andaccordingly, it is apparent that the charged particles in the pelletsare not electrons or holes but ions, more specifically, protons inconsideration of the configuration of the fullerene derivative.

[0206] The conductivity of the above-described charged particles can becalculated on the basis of an intercept of the circular-arc on the highfrequency side with the X-axis. For the pellet 1A of Inventive Example4, the conductivity of the charged particles become about 1×10⁻⁶ S/cm.The pellets of 1B of Inventive Example 4, the pellets 2A and 2B ofInventive Example 5, and the pellets of 3A and 3B of Inventive Example 6were subjected to the same measurement as described above. As a result,the whole shape of the frequency characteristics of the impedance ineach of the pellets 1B, 2A and 2B, and 3A and 3B is similar to that of1A of Inventive Example 4; however, as shown in Table 2, theconductivity of charged particles in each of the pellets of 1B, 2A and2B, and 3A and 3B, obtained on the basis of an intercept of acircular-arc portion with the X-axis, is different from that in thepellet 1A. TABLE 2 Conductivities of Pellets of Proton Conductors inInventive Examples 4, 5 and 6 (at 25° C.) Kind of Pellets Conductivity(S/cm) Pellet 1A of Inventive Example 4 1 × 10⁻⁶ Pellet 2A of InventiveExample 5 2 × 10³¹ ⁴ Pellet 3A of Inventive Example 6 6 × 10⁻⁵ Pellet 1Bof Inventive Example 4 3 × 10⁻⁶ Pellet 2B of Inventive Example 5 7 ×10⁻⁴ Pellet 3B of Inventive Example 6 3 × 10⁻⁶

[0207] As shown in Table 2, in both of the pellet types A and B of theInventive Examples 4, 5, and 6, the conductivity of the pellet of thefullerene derivative containing the OSO₃H groups is larger than that ofthe pellet of the fullerene derivative containing the hydroxyl groups.The reason for this is that the OSO₃H groups cause ionization ofhydrogen more easily than the hydroxyl groups. The results of Table 2also show that the aggregate of the fullerene derivative containing thehydroxyl groups and OSO₃H groups can exhibit, in a dry atmosphere, agood proton conductivity at ordinary temperature.

[0208] Next, the complex impedance of the pellet 1A of Inventive Example4 was measured in a temperature range from 160° C. to −40° C., and theconductivity of the pellet was calculated on the basis of a circular-arcportion on the high frequency side of the complex impedance curve of thepellet measured at each temperature to examine the temperaturedependency on the conductivity. The results are shown in FIG. 15 as theArrhenius plot. From the data shown in FIG. 15, it is apparent that theconductivity and temperature exist in a linear relationship at leastwithin the temperature range of 160° C. to −40° C. In other words, dataof FIG. 15 shows that a single ion conduction mechanism can proceed inthe temperature range of 160° C. to −40° C. The proton conductor mainlycontaining the fullerene derivative and a polymer material according tothe present invention, therefore, can exhibit a good proton conductivityin a wide temperature range including ordinary temperature,particularly, ranging from a high temperature of 160° C. to a lowtemperature of −40° C.

[0209] III. Carbon Cluster Derivative

[0210] <Production (Part 1) of Carbon Cluster Derivative>

[0211] Arc discharge was performed by applying a current of 200 Abetween both electrodes composed of carbon bars in 0.05 MPa of an argon,to thus obtain 1 g of a carbon powder. The carbon powder was mixed with100 ml of 60% fuming sulfuric acid, and kept for three days in anitrogen flow at 60° C. The heating was performed by using a water bath.The reaction solution was dropped little by little in 500 ml of purewater, and a solid matter was separated from the water solution bycentrifugal separation method. The solid matter was cleaned severaltimes by diethyl ether anhydride, and dried for five hours under areduced pressure at 40° C. The resultant powder was dissolved in 10 mlof tetrahydrofurane (THP), an insoluble component removed by filtering,and the solvent was evaporated under a reduced pressure to obtain asolid matter wherein the solid matter of 50 mg was pressed at a force of7 tons/cm² into a circular pellet having a diameter of 15 mm. Such apellet is taken as a pellet of Inventive Example 7.

[0212] <Measurement of Proton Conductivity of Pellet of Carbon ClusterDerivative>

[0213] The AC impedance of the pellet of Inventive Example 7 wasmeasured in a dry air in accordance with the same manner as describedabove. As a result, it was confirmed that an impedance behaviorresulting from ion conductance appeared in a frequency region of 10 MHzor less. The conductivity of the pellet of Inventive Example 7 wascalculated, on the basis of the diameter of a circular-arc curve of theimpedance behavior, at 3.0×10⁻⁴ (S/cm).

[0214] <Production (Part 2) of Carbon Cluster Derivative>

[0215] Arc discharge was performed by applying a current of 200 Abetween both electrodes composed of carbon bars in 0.05 MPa of an argongas, to thus obtain 1 g of a carbon powder. The carbon powder wasdissolved in toluene, an insoluble component was removed by filtering,and the solvent was evaporated under a reduced pressure to obtain apowder again. The resultant powder was mixed with 100 ml of 60% fumingsulfuric acid, and kept for three days under a nitrogen flow at 60° C.The heating was performed by using a water bath. The reaction solutionwas dropped little by little in 500 ml of pure water, and a solid matterwas separated from the water solution by centrifugal separation method.The solid matter was cleaned several times by diethyl ether anhydride,and dried for five hours under a reduced pressure at 40° C. The solidmatter of 50 mg was under a force of 7 tons/cm² into a circular pelletof Inventive Example 8.

[0216] <Measurement of Proton Conductivity of Pellet of Carbon ClusterDerivative>

[0217] The AC impedance of the pellet of Inventive Example 8 wasmeasured in a dry air in accordance with the same manner as describedabove. As a result, it was confirmed that an impedance behaviorresulting from ion conductance appeared in a frequency region of 10 MHzor less. The conductivity of the pellet of Inventive Example 8 wascalculated, on the basis of the diameter of a circular-arc curve of theimpedance behavior, at 3.4×10⁻⁴ (S/cm).

[0218] The main component of the carbon powder obtained by arc dischargewas carbon clusters or molecules of carbon clusters not having a closedstructure, such as, a cage structure, but having a structure at leastpart of which has open ends. In addition, molecules having a structurewith good electronic conductivity, similar to the graphite structure,which are slightly contained in the carbon cluster molecules, oftenobstruct the function of the ionic conductor and thereby they areremoved after acid treatment in Inventive Example 7 and directly afterarc discharge in Inventive Example 8. As a result, it was confirmed bythe AC impedance method that the pellet has no electronic conductivity.FIG. 16 shows the TOF-MS spectrum of carbon powder obtained by arcdischarge. As shown in FIG. 16, most of the carbon powder has a massnumber of 5500 or less, that is, the carbon number of 500 or less. Sincethe carbon-carbon bonding distance of the carbon powder is less than 2Å, the diameter of each of the carbon clusters of the powder is lessthan 100 nm.

[0219] IV. Tubular Carbonaceous Material Derivative

[0220] <Synthesis (Part 1) of a Polyhydroxylated SWCNT Material>

[0221] A refined SWCNT material was prepared and then burned for tenhours at 250° C. under a fluorine gas in order to obtain polyfluorinatedSWCNT. The polyfluorinated SWCNT was placed in pure water and refluxedfor three days at 100° C. while being strongly stirred in order tosubstitute the fluorine atoms for hydroxyl groups thereby resulting inthe polyhydroxylated SWCNT material which is identified as a material inInventive Example 9.

[0222] <Synthesis of Hydrogen Sulfated SWCNT>

[0223] Polyhydroxylated SWCNT produced in the same manner as that inInventive Example 9 was placed in fuming sulfuric acid and stirred forthree days at 60° C. in order to replace the hydroxyl groups with theOSO₃H groups thereby resulting in the hydrogen sulfated SWCNT materialas identified in Inventive Example 10.

[0224] <Synthesis (Part 2) of Polyhydroxylated SWCNT>

[0225] A refined SWCNT material was prepared and then subjected tooxygen plasma treatment. Then, the atmosphere in the chamber wasreplaced with hydrogen and the material was subsequently subjected tohydrogen plasma treatment in order to obtain the polyhydroxylated SWCNTmaterial as identified as Inventive Example 11.

[0226] <Production of Sample Films>

[0227] Each of the above three materials was dispersed in water and thedispersion was filtered on a filter paper having pores of 0.2 μm bysuction in order to deposit the film on the filter paper. The amount ofthe dispersion to be filtered was adjusted to form the film having athickness of 100 μm. The film deposited on the filter paper could beeasily peeled therefrom. These films thus obtained are taken as films inInventive Examples 9, 10 and 11. A material obtained by mixing thematerial in Inventive Example 10 with a poly-hydrogen-sulfated fullerenederivative at a weight ratio of 1:1 was filtered in the same manner asdescribed above to form a film as identified in Inventive Example 12.Further, an SWCNT material that contains no functional groups wasfiltered in the same manner as described above to form the film which isidentified as Comparative Example 4.

[0228] <Measurement of Proton Conductivities of the Film>

[0229] To measure a proton conductivity of each of the films inInventive Examples 9 to 12 and Comparative Example 4 both sides of thefilm were held between aluminum foil which were cut into a disc shapehaving a diameter 15 mm. The disc was held between electrodes, and ACvoltages (amplitude: 0.1 V) at frequencies ranging from 7 MHz to 0.01 Hzwere applied to the film to measure a complex impedance at eachfrequency. The measurement was performed under a dry atmosphere.

[0230] The measurement result of the film in Comparative Example 4 willbe described below. The complex impedance of the film was fixed at a lowresistance, that is, was not changed over the above frequency range dueto the fact that the electronic conductivity of the SWCNT material ofComparative Example 4 is high.

[0231] As a result, it was revealed that the film in Comparative Example4 cannot be used as an ionic conductor.

[0232] The measurement results of the films in Inventive Examples 9-12will be described below. A complex impedance of the film of InventiveExample 10 is representatively shown in FIG. 26. Referring to FIG. 26,the impedance in a high frequency region depicts a flattened but verysmooth semi-circular curve, which shows the conductance of some chargedparticles in the film and the imaginary number portion of the impedanceis rapidly raised in a low frequency region, which shows the occurrenceof the blocking of charged particles between the aluminum electrodes andthe film as gradually nearing to a DC voltage.

[0233] With respect to the blocking of the charged particles between thealuminum electrode and the film in Inventive Example 10, the chargedparticles on the aluminum electrode side are electrons, and accordingly,it is apparent that the charged particles in the film are not electronsor holes but ions, more specifically, protons in considering of thestructure of the tubular carbonaceous derivative that forms the film.

[0234] With respect to the films in Inventive Examples 9, 11 and 12, thebehavior of these films are similar to that of the film in InventiveExample 10 as observed although there was a difference in the size ofthe circular arc therebetween. Accordingly, it was revealed that thefilms in Inventive Examples 9-12 desirably function as a tubularcarbonaceous material derivative of a proton conductor.

[0235] With respect to the above impedance measurements, the protonconducting portion 1 of the film-like proton conductor constitutes anelectrically equivalent circuit in which a capacitance is formed betweenfirst and second electrodes with a resistance in the proton conductingportion held therebetween as similarly identified in the previouslydiscussed embodiments and as further illustrated in FIG. 10A. Inaddition, the capacitance designates a delay effect (phase delay at ahigh frequency) upon migration of protons, and the resistance designatesa parameter of difficulty of migration of protons. The measuredimpedance Z is expressed by the equation as previously discussed inother embodiments. The frequency dependency on the proton conductivityportion was examined.

[0236] The conductivity of the above described charged particles can becalculated on the basis of an intercept of the circular-arc on the highfrequency side of with the X-axis. The conductivity of the film inInventive Example 10 is about 2×10⁻⁵ S/cm. The conductivities of thefilm in Inventive Examples 9, 11, and 12 are 2×10⁻⁷ S/cm, 7×10⁻⁸ (S/cm)and 8×10⁻⁴ (S/cm), respectively. The conductivity for each of InventiveExamples 9-12 were measure at 25° C.

[0237] In comparing the conductivity of Inventive Examples 9-12, it isapparent that the tubular carbonaceous material derivative that containthe hydrogen sulfated functional groups, i.e. the —OSO₃H groups, arelarger than the conductivity of the tubular carbonaceous materialderivative that contain the hydroxyl groups. The reason for thisdifference was discussed in relation to previous embodiment of thepresent invention. The comparison of Inventive Examples 9-12 alsodemonstrates that the aggregate of the tubular carbonaceous materialderivative that contains either or both of the hydroxyl and hydrogensulfated groups, even in a dry atmosphere, desirably displays a protonconductivity at ordinary temperatures.

[0238] As is apparent from the above description, since the first protonconductor according to the first embodiment mainly contains a fullerenederivative that includes functional groups, it can exhibit a high protonconductivity, even in a dry state, in a wide temperature range includingordinary temperature. Since the electrochemical device using the firstproton conductor is not limited by an atmosphere, its construction canbe simplified and minimized in size.

[0239] Since the first proton conductor can be produced of a fullerenederivative, it is possible to efficiently produce the first protonconductor without use of any binder resin, and hence to enhance theproton conductivity of the first proton conductor and reduce the weightthereof.

[0240] Since the second proton conductor according to the secondembodiment can be obtained by mixing the fullerene derivative with apolymer material, a high film formation ability can be given, togetherwith the above performance of the first proton conductor, to the secondproton conductor, so that the second proton conductor can be used as athin film having a high strength, a good gas permeation preventativeability and a high proton conductivity. The electrochemical device, suchas, a fuel cell using the second proton conductor has a performancecomparable to that of the electrochemical device using the first protonconductor, and also exhibits the effect of the second proton conductorin the form of a thin film.

[0241] Since the third proton conductor according to the thirdembodiment mainly contains a carbon cluster derivative in whichfunctional groups are introduced to each of the carbon clusters whichare the base material of the carbon cluster derivative, it can exhibiteffects similar to those obtained by each of the first and secondembodiments in terms of proton conductivity, operation temperature,simplification of the system, miniaturization and economy. Further,since each carbon cluster contains a large number of carbon atomsclosely bonded to each other, it is less susceptible to deterioration byoxidation, and is advantageous in that the selection range of the rawmaterial can be extended.

[0242] Since the fourth proton conductor according to the fourthembodiment mainly contains a tubular carbonaceous material derivativethat includes a number of functional groups, this type of protonconductor can exhibit desirable effects that are similar to those whichwere demonstrated and obtained by each of the first, second and thirdembodiments with regards to proton conductivity, operation temperature,simplification of construction, miniaturization, and economy for a fuelcell using the proton conductor. Further, according to the presentinvention as detailed in the fourth embodiment, a tubular carbonaceousmaterial derivative film that has high strength and good protonconductivity is desirably suitable for an electrochemical device, inparticular, a fuel cell. This film can be obtained by dispersing thetubular carbonaceous material derivative in a liquid and filtering thedispersion.

[0243] Although modifications and changes may be suggested by thoseskilled in the art, it is the intention of the inventors to embodywithin the patent warranted hereon all changes and modifications asreasonably and properly come within their contribution to the art.

We claim as our invention:
 1. A proton conductor comprising a carboncluster derivative that comprises a plurality of functional groups so asto be capable of transferring a plurality of protons between each of thefunctional groups of the carbon cluster derivative.
 2. A protonconductor according to claim 1, wherein the carbon cluster derivativecomprises a plurality of clusters that each have a length along a majoraxis of 100 nm or less and two or more functional groups.
 3. A protonconductor according to claim 1, wherein the carbon cluster derivativecomprises a plurality of clusters that each have a cage structure or astructure at least part of which has open ends.
 4. A proton conductoraccording to claim 1, wherein said carbon cluster derivative comprises afullerene molecule that includes a spherical carbon cluster expressed byC_(m) where m comprises 36, 60, 70, 78, 82 or
 84. 5. A proton conductoraccording to claim 1, wherein said carbon cluster derivativesubstantially comprises a plurality of carbon clusters.
 6. A protonconductor according to claim 1, wherein the functional groups areexpressed by —XH where X represents an arbitrary atom or an atomic groupthat has a bivalent bond and where H represents a hydrogen atom.
 7. Aproton conductor according to claim 1, wherein the functional groups areexpressed by —OH or —YOH where Y is an arbitrary atom or an atomic grouphaving a bivalent bond, where O represents an oxygen atom, and where Hrepresents a hydrogen atom.
 8. A proton conductor according to claim 7,wherein the functional groups are selected from the group consisting of—OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 9. A proton conductoraccording to claim 1, wherein the carbon cluster derivative furthercomprises a plurality of electron attractive groups in addition to thefunctional groups.
 10. A proton conductor according to claim 9, whereinthe electron attractive groups are selected from the group consisting ofnitro groups, carbonyl groups, carboxyl groups, nitrile groups, alkylhalide groups, and halogen atoms.
 11. A proton conductor according toclaim 1, wherein said proton conductor substantially comprises thecarbon cluster derivative.
 12. A proton conductor according to claim 1,wherein the proton conductor further comprises a polymer material inaddition to the carbon cluster derivative.
 13. A proton conductoraccording to claim 12, wherein the polymer material has no electronicconductivity.
 14. A proton conductor according to claim 12 wherein thepolymer material, comprises a plurality of polymer material compoundsthat are selected from the group consisting of polyfluoroethylene,polyvinylidene fluoride, and polyvinylalcohol.
 15. A proton conductoraccording to claim 12, wherein the polymer material comprises 20 wt % orless.
 16. A proton conductor according to claim 12, wherein the polymermaterial comprises polyfluoroethylene of 3 wt % or less.
 17. A protonconductor according to claim 12, wherein the proton conductor comprisesa thin film that has a thin film thickness of 300 μm or less.
 18. Amethod of producing a proton conductor, comprising the steps of: forminga carbon powder by producing a plurality of carbon clusters that eachinclude a plurality of carbon atoms by an arc discharge technique thatutilizes a carbon-based electrode; subjecting the carbon powder to anacid treatment; and introducing a plurality of functional groups to thecarbon powder so as the carbon powder is capable of transferring protonsbetween each of the functional groups of the carbon powder.
 19. A methodof producing a proton conductor according to claim 18, furthercomprising the steps of forming a carbon cluster derivative byintroducing the functional groups to the carbon powder, and compactingthe carbon cluster derivative into a desired shape.
 20. A method ofproducing a proton conductor according to claim 18, wherein thecompacting step comprises the step of forming the carbon clusterderivative into a pellet shape without the use of any binder.
 21. Amethod of producing a proton conductor according to claim 18, whereinthe functional groups are represented by —XH where X is an arbitraryatom or an atomic group that has a bivalent bond and where H is ahydrogen atom.
 22. A method of producing a proton conductor according toclaim 18, wherein the functional groups are expressed by —OH or —YOHwhere Y is an arbitrary atom or an atomic group that has a bivalentbond, where O is an oxygen atom and where H is a hydrogen atom.
 23. Amethod of producing a proton conductor according to claim 22, whereinthe functional groups are selected from the group consisting of —OH,—OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 24. A method of producing a protonconductor according to claim 18, further comprising the step ofintroducing a plurality of electron attractive groups to the carbonpowder in addition to the functional groups.
 25. A method of producing aproton conductor according to claim 24, wherein the electron attractivegroups are selected from the group consisting of nitro groups, carbonylgroups, carboxyl groups, nitrile groups, alkyl halide groups and halogenatoms.
 26. A method of producing a proton conductor according to claim18, wherein the carbon powder comprises a cluster that substantiallyincludes a plurality of carbon atoms, the cluster comprises a lengthalong a major axis of 100 nm or less, and wherein two or more functionalgroups are introduced to the cluster.
 27. A method of producing a protonconductor according to claim 18, wherein the carbon powder comprises aspherical carbon cluster that is expressed by C_(m) wherein m represents36, 60, 70, 78 or
 82. 28. A method of producing a proton conductoraccording to claim 18, wherein the carbon powder comprises a clusterthat has a cage structure or a structure at least part of which has openends.
 29. A method of producing a proton conductor according to claim18, further comprising the step of mixing the carbon powder with apolymer material so as to form a thin film or a pellet construction. 30.A method of producing a proton conductor according to claim 29, whereinthe polymer material comprises no electronic conductivity.
 31. A methodof producing a proton conductor according to claim 29, wherein thepolymer material comprises a polymer material compound that is selectedfrom the group consisting of at least one of polyfluoroethylene,polyvinylidene fluoride, and polyvinylalcohol.
 32. A method of producinga proton conductor according to claim 29, wherein the polymer materialcomprises 20 wt % or less.
 33. A method of producing a proton conductoraccording to claim 29, wherein the polymer material comprisespolyfluoroethylene of 3 wt % or less.
 34. A method of producing a protonconductor according to claim 29, wherein the proton conductor comprisesa thin film that has a thickness of 300 μm or less.
 35. Anelectrochemical device comprising a first electrode, a second electrode,and a proton conductor that is positioned between the first and secondelectrodes, the proton conductor comprising a carbon cluster derivativethat comprises a plurality of functional groups so as to be capable oftransferring a plurality of protons between each of the functionalgroups of the carbon cluster derivative.
 36. An electrochemical deviceaccording to claim 35, wherein the carbon cluster derivative comprises acluster that substantially contains a plurality of carbon atoms, thecluster comprises a length along a major axis of 100 nm or less andwherein the cluster comprises two or more functional groups.
 37. Anelectrochemical device according to claim 36, wherein the carbon clusterderivative comprises a cluster that has a cage structure or a structureat least part of which has open ends.
 38. An electrochemical deviceaccording to claim 35, wherein the functional groups are expressed by—XH where X is an arbitrary atom or an atomic group that has a bivalentbond and where H is a hydrogen atom.
 39. An electrochemical deviceaccording to claim 35, wherein the functional groups are selected fromthe group consisting of —OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 40. Anelectrochemical device according to claim 35, wherein the protonconductor further comprises a plurality of electron attractive groups inaddition to the functional groups.
 41. An electrochemical deviceaccording to claim 40, wherein the electron attractive groups areselected from the group consisting of nitro groups, carbonyl groups,carboxyl groups, nitrile groups, alkyl halide groups and halogen atoms.42. An electrochemical device according to claim 35, wherein the carboncluster derivative comprises a spherical carbon cluster that isexpressed by C_(m) where m represents 36, 60, 70, 78, 82 or
 84. 43. Anelectrochemical device according to claim 35, wherein the protonconductor substantially comprises the carbon cluster derivative whichincludes a plurality of clusters that each mainly contain carbon atoms.44. An electrochemical device according to claim 35, wherein the carboncluster derivative comprises a fullerene molecule.
 45. Anelectrochemical device according to claim 44, wherein the fullerenemolecule is a spherical carbon cluster material that is expressed byC_(m) where m represents 36, 60, 70, 78, 82 or
 84. 46. Anelectrochemical device according to claim 35, wherein the protonconductor further comprises a polymer material.
 47. An electrochemicaldevice according to claim 46, wherein the polymer material has noelectron conductivity.
 48. An electrochemical device according to claim46, wherein the polymer material comprises a polymer material compoundthat is selected from the group consisting of at least one ofpolyfluoroethylene, polyvinylidene fluoride, and polyvinylalcohol. 49.An electrochemical device according to claim 46, wherein the polymermaterial comprises 20 wt % or less.
 50. An electrochemical deviceaccording to claim 46, wherein the polymer material comprisespolyfluoroethylene of 3 wt % or less.
 51. An electrochemical deviceaccording to claim 35, wherein the proton conductor comprises a thinfilm that has a thickness of 300 μm or less.
 52. An electrochemicaldevice according to claim 35, wherein each of the first and secondelectrodes comprise a gas electrode.
 53. An electrochemical deviceaccording to claim 52, wherein the electrochemical device comprises afuel cell.
 54. An electrochemical device according to claim 52, whereinthe electrochemical device comprises a hydrogen-air fuel cell.
 55. Anelectrochemical device according to claim 52, wherein one of the firstor second electrodes comprises a gas electrode.
 56. An electrochemicaldevice according to claim 35, wherein each of the first and secondelectrodes comprise an active electrode.
 57. An electrochemical deviceaccording to claim 35, wherein at least one of the first and secondelectrodes comprises an active electrode.
 58. A proton conductorcomprising a fullerene derivative that comprises a plurality offunctional groups so as to be capable of transferring hydrogen protonsbetween the functional groups of the fullerene derivative.
 59. A protonconductor according to claim 58, wherein the functional groups areexpressed by —XH where X is an arbitrary atom or an atomic group thathas a bivalent bond and where X is a hydrogen atom.
 60. A protonconductor according to claim 58, wherein the functional groups areexpressed by —OH or —YOH where Y is an arbitrary atom or an atomic groupthat has a bivalent bond, where O is an oxygen atom and where H is ahydrogen atom.
 61. A proton conductor according to claim 58, wherein thefunctional groups are selected from the group consisting of —OH, —OSO₃H,—COOH, —SO₃H, and —OPO(OH)₃.
 62. A proton conductor according to claim58, wherein the proton conductor further comprises a plurality ofelectron attractive groups in addition to the functional groups.
 63. Aproton conductor according to claim 62, wherein the electron attractivegroups are selected from a group consisting of nitro groups, carbonylgroups, carboxyl groups, nitrile groups, alkyl halide groups and halogenatoms.
 64. A proton conductor according to claim 58, wherein thefullerene derivative comprises a fullerene molecule that has a sphericalcarbon cluster expressed by C_(m) where m represents 36, 60, 70, 78, 82or
 84. 65. A proton conductor according to claim 58, wherein the protonconductor substantially comprises the fullerene derivative.
 66. A methodof producing a proton conductor, comprising the steps of: producing afullerene derivative by introducing a plurality of functional groups toa plurality of fullerene molecules of the fullerene derivative; forminga powder of the fullerene derivative; and compacting the powder into adesired shape.
 67. A method or producing a proton conductor according toclaim 66, wherein the compacting step comprises the step of forming apowder of the fullerene derivative into a pellet without the use of anybinder.
 68. A method or producing a proton conductor according to claim66, wherein the functional groups are expressed by —XH where X is anarbitrary atom or an atomic group that has a bivalent bond and where His a hydrogen atom.
 69. A method or producing a proton conductoraccording to claim 66, wherein the functional groups are expressed by—OH or —YOH where Y is an arbitrary atom or an atomic group that hasbivalent bond, where O is an oxygen atom and where H is a hydrogen atom.70. A method or producing a proton conductor according to claim 69,wherein the functional groups are selected from the group consisting of—OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 71. A method or producing aproton conductor according to claim 70, wherein the step of producingthe fullerene derivative further comprises the step of introducing aplurality of electron attractive groups to the fullerene molecules ofthe fullerene derivative in addition to the functional groups.
 72. Amethod or producing a proton conductor according to claim 71, whereinthe electron attractive groups are selected from the group consisting ofnitro groups, carbonyl groups, carboxyl groups, nitrile groups, alkylhalide groups and halogen atoms.
 73. A method or producing a protonconductor according to claim 66, wherein the fullerene derivativecomprises a spherical carbon cluster expressed by C_(m) where mrepresents 36, 60, 70, 78, 82 or
 84. 74. A electrochemical devicecomprising a first electrode, a second electrode and a proton conductorthat is positioned between the first and second electrodes, the protonconductor comprising a fullerene derivative that comprises a pluralityof functional groups so as to be capable of transferring protons betweenthe functional groups of the fullerene derivative.
 75. Anelectrochemical device according to claim 74, wherein the functionalgroups are expressed by —XH where X is an arbitrary atom or an atomicgroup that has a bivalent bond and where H is a hydrogen atom.
 76. Anelectrochemical device according to claim 74, wherein the functionalgroups are expressed by —OH or —YOH where Y is an arbitrary atom or anatomic group that has bivalent bond, where O is an oxygen atom and whereH is a hydrogen atom.
 77. An electrochemical device according to claim74, wherein the functional groups are selected from the group consistingof —OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 78. An electrochemicaldevice according to claim 74, wherein the proton conductor furthercomprises a plurality of electron attractive groups in addition to thefunctional groups.
 79. An electrochemical device according to claim 78,wherein the electron attractive groups are selected from the groupconsisting of nitro groups, carbonyl groups, carboxyl groups, nitrilegroups, alkyl halide groups and halogen atoms.
 80. An electrochemicaldevice according to claim 74, wherein the fullerene derivative comprisesa fullerene molecule that includes a spherical carbon cluster which isexpressed by C_(m) where m represents 36, 60, 70, 78, 82 or
 84. 81. Anelectrochemical device according to claim 74, wherein the protonconductor substantially comprises the fullerene derivative.
 82. Anelectrochemical device according to claim 74, wherein each of the firstand second electrodes comprise a gas electrode.
 83. An electrochemicaldevice according to claim 82, wherein the electrochemical devicecomprises a fuel cell.
 84. An electrochemical device according to claim82, wherein the electrochemical device comprises a hydrogen-air fuelcell.
 85. An electrochemical device according to claim 74, wherein oneof the first or second electrodes comprise a gas electrode.
 86. Anelectrochemical device according to claim 74, wherein each of the firstand second electrodes comprise an active electrode.
 87. Anelectrochemical device according to claim 74, wherein at least one ofthe first and second electrodes comprises an active electrode.
 88. Aproton conductor comprising a fullerene derivative and a polymermaterial, the fullerene derivative comprising a plurality of functionalgroups so as to be capable of transferring protons between thefunctional groups of the fullerene derivative.
 89. A proton conductoraccording the claim 88, wherein the functional groups are expressed by—XH where X is an arbitrary atom or an atomic group that has a bivalentbond and where H is a hydrogen atom.
 90. A proton conductor accordingthe claim 88, wherein the functional groups are expressed by —OH or —YOHwhere Y is an arbitrary atom or an atomic group that has bivalent bond,where O is an oxygen atom and where H is a hydrogen atom.
 91. A protonconductor according the claim 90, wherein the functional groups comprise—OH, —OSO₃H, —COOH, —SO₃H, or —OPO(OH)₃.
 92. A proton conductoraccording the claim 88, wherein the fullerene derivative furthercomprises a plurality of electron attractive groups in addition to thefunctional groups.
 93. A proton conductor according the claim 92,wherein the electron attractive groups are selected from the groupconsisting of nitro groups, carbonyl groups, carboxyl groups, nitrilegroups, alkyl halide groups and halogen atoms.
 94. A proton conductoraccording the claim 88, wherein the fullerene derivative comprises aspherical carbon cluster expressed by C_(m) where m represents 36, 60,70, 78, 82 or
 84. 95. A proton conductor according the claim 88, whereinthe polymer material comprises a polymer material compound that isselected from the group consisting of at least one ofpolyfluoroethylene, polyvinylidene fluoride, and polyvinylalcohol; orwherein the polymer material has no electron conductivity.
 96. A protonconductor according the claim 88, wherein the polymer material comprises20 wt % of less.
 97. A proton conductor according the claim 88, whereinthe polymer material comprises polyfluoroethylene of 3 wt % or less. 98.A proton conductor according to claim 88, wherein the proton conductorcomprises a thin film that has a thickness of 300 μm or less.
 99. Amethod of producing a proton conductor comprising the steps of:producing a fullerene derivative by introducing a plurality offunctional groups to a plurality of fullerene molecules of the fullerenederivative; mixing the fullerene derivative with a polymer material; andforming the fullerene derivative and polymer material mixture into athin film.
 100. A method of producing a proton conductor according toclaim 99, wherein the polymer material has no electronic conductivity.101. A method of producing a proton conductor according to claim 99,wherein the functional groups are expressed by —XH where X is anarbitrary atom or an atomic group that has a bivalent bond and where His a hydrogen atom.
 102. A method of producing a proton conductoraccording to claim 99, wherein the functional groups are expressed by—OH or —YOH where Y is an arbitrary atom or an atomic group that hasbivalent bond, where O is an oxygen atom and where H is a hydrogen atom.103. A method of producing a proton conductor according to claim 102,wherein the functional groups are selected from the group consisting of—OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 104. A method of producing aproton conductor according to claim 99, wherein a plurality of electronattractive groups are further introduced to the fullerene derivative inaddition to the functional groups.
 105. A method of producing a protonconductor according to claim 104, wherein the electron attractive groupsare selected from the group consisting of at least one of nitro groups,carbonyl groups, carboxyl groups, nitrile groups, alkyl halide groupsand halogen atoms.
 106. A method of producing a proton conductoraccording to claim 99, wherein the fullerene derivative comprises aspherical carbon cluster material expressed by C_(m) where m represents36, 60, 70, 78, 82 or
 84. 107. A method of producing a proton conductoraccording to claim 99, wherein the polymer material comprises a polymermaterial compound that is selected from the group consisting ofpolyfluoroethylene, polyvinylidene fluoride, and polyvinylalcohol. 108.A method of producing a proton conductor according to claim 99, whereinthe polymer material comprises 20 wt % or less.
 109. A method ofproducing a proton conductor according to claim 99, wherein the polymermaterial comprises polyfluoroethylene of 3 wt % or less.
 110. A methodof producing a proton conductor according to claim 99, wherein theproton conductor comprises a thin film that has a thickness of 300 μm orless.
 111. An electrochemical device comprising a first electrode, asecond electrode, a proton conductor and a polymer material that areheld between the first and second electrodes, the proton conductorcomprising a fullerene derivative that comprises a plurality offunctional groups so as to be capable of transferring protons betweenthe functional groups of the fullerene derivative.
 112. Anelectrochemical device according to claim 111, wherein the polymermaterial has no electron conductivity.
 113. An electrochemical deviceaccording to claim 111, wherein the functional groups are expressed by—XH where X is an arbitrary atom or an atomic group that has a bivalentbond and where H is a hydrogen atom.
 114. An electrochemical deviceaccording to claim 111, wherein the functional groups are expressed by—OH or —YOH where Y is an arbitrary atom or an atomic group that hasbivalent bond, where O is an oxygen atom and where H is a hydrogen atom.115. An electrochemical device according to claim 114, wherein thefunctional groups are selected from the group consisting of at least oneof —OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 116. An electrochemicaldevice according to claim 111, wherein the fullerene derivative furthercomprises a plurality of electron attractive groups in addition to thefunctional groups.
 117. An electrochemical device according to claim116, wherein the electron attractive groups are selected from the groupconsisting of nitro groups, carbonyl groups, carboxyl groups, nitrilegroups, alkyl halide groups and halogen atoms.
 118. An electrochemicaldevice according to claim 111, wherein the fullerene derivativecomprises a spherical carbon cluster which is expressed by C_(m) where mrepresents 36, 60, 70, 78, 82 or
 84. 119. An electrochemical deviceaccording to claim 111, wherein the polymer material comprises a polymermaterial compound that is selected from the group consisting ofpolyfluoroethylene, polyvinylidene fluoride, and polyvinylalcohol. 120.An electrochemical device according to claim 111, wherein the polymermaterial comprises 20 wt % or less.
 121. An electrochemical deviceaccording to claim 111, wherein the polymer material comprisespolyfluoroethylene of 3 wt % or less.
 122. An electrochemical deviceaccording to claim 111, wherein the proton conductor comprises a thinfilm that has a thickness of 300 μm or less.
 123. An electrochemicaldevice according to claim 111, wherein each of the first and secondelectrodes comprise a gas electrode.
 124. An electrochemical deviceaccording to claim 123, wherein the electrochemical device comprises afuel cell.
 125. An electrochemical device according to claim 124,wherein the electrochemical device comprises a hydrogen-air fuel cell.126. An electrochemical device according to claim 111, wherein one ofthe first and second electrodes comprise a gas electrode.
 127. Anelectrochemical device according to claim 111, wherein each of the firstand second electrodes comprise an active electrode.
 128. Anelectrochemical device according to claim 111, wherein at least one ofthe first and second electrodes comprise an active electrode.
 129. Aproton conductor comprising a tubular carbonaceous material derivativethat comprises a plurality of functional groups so as to be capable oftransferring protons between the functional groups of the tubularcarbonaceous material derivative.
 130. A proton conductor according toclaim 129, wherein the functional groups are expressed by —XH where X isan arbitrary atom or an atomic group that has a bivalent bond and whereH is a hydrogen atom.
 131. A proton conductor according to claim 129,wherein the functional groups comprise —OH or —YOH where Y is anarbitrary atom or an atomic group that has bivalent bond, where O is anoxygen atom and where H is a hydrogen atom.
 132. A proton conductoraccording to claim 129, wherein the functional groups are selected fromthe group consisting of —OH, —OSO₃H, —COOH, —SO₃H, and —OPO(OH)₃.
 133. Aproton conductor according to claim 129, wherein the tubularcarbonaceous material derivative further comprises a plurality ofelectron attractive groups in addition to the functional groups.
 134. Aproton conductor according to claim 133, wherein the electron attractivegroups are selected from the group consisting of nitro groups, carbonylgroups, carboxyl groups, nitrile groups, alkyl halide groups and halogenatoms.
 135. A proton conductor according to claim 129, wherein thetubular carbonaceous material derivative comprises a tubularcarbonaceous material that is a single wall carbon nano-tube material.136. A proton conductor according to claim 129, wherein the tubularcarbonaceous material derivative comprises a tubular carbonaceousmaterial that is a multi-wall carbon nano-tube material.
 137. A protonconductor according to claim 129, wherein the tubular carbonaceousmaterial derivative comprises a tubular carbonaceous material that is acarbon nano-fiber material.
 138. A proton conductor according to claim129, wherein the proton conductor comprises a mixture of the tubularcarbonaceous material derivative and a fullerene derivative that alsoincludes the functional groups.
 139. A method of producing a protonconductor, comprising the steps of: preparing one of a halogenated ornon-halogenated tubular carbonaceous material as a raw material; andforming a tubular carbonaceous material derivative by introducing aplurality of functional groups onto the raw material by subjecting theraw material to hydrolysis or an acid treatment or hydrolysis and anacid treatment or a plasma treatment.
 140. A method of producing aproton conductor according to claim 139, further comprising subjectingthe halogenated tubular carbonaceous material to hydrolysis or an acidtreatment or hydrolysis and an acid treatment so as to form the tubularcarbonaceous material derivative or subjecting the non-halogenatedtubular carbonaceous material to the plasma treatment so as to form thetubular carbonaceous material derivative.
 141. A method of producing aproton conductor according to claim 139, wherein the functional groupsare expressed by —XH where X is an arbitrary atom or an atomic groupthat has a bivalent bond and where H is a hydrogen atom.
 142. A methodof producing a proton conductor according to claim 139, wherein thefunctional groups comprise —OH or —YOH where Y is an arbitrary atom oran atomic group that has bivalent bond, where O is an oxygen atom andwhere H is a hydrogen atom.
 143. A method of producing a protonconductor according to claim 142, wherein the functional groups areselected from the group consisting of —OH, —OSO₃H, —COOH, —SO₃H, and—OPO(OH)₃.
 144. A method of producing a proton conductor according toclaim 139, further comprising introducing a plurality of electronattractive groups in addition to the functional groups to the tubularcarbonaceous material of the tubular carbonaceous material derivative.145. A method of producing a proton conductor according to claim 144,wherein the electron attractive groups are selected from the groupconsisting of nitro groups, carbonyl groups, carboxyl groups, nitrilegroups, alkyl halide groups and halogen atoms.
 146. A method ofproducing a proton conductor according to claim 139, wherein the tubularcarbonaceous material derivative comprises a tubular carbonaceousmaterial that includes a single-wall carbon nano-tube material.
 147. Amethod of producing a proton conductor according to claim 139, whereinthe tubular carbonaceous material derivative comprises a tubularcarbonaceous material that includes a multi-wall carbon nano-tubematerial.
 148. A method of producing a proton conductor according toclaim 139, wherein the tubular carbonaceous material derivativecomprises a tubular carbonaceous material that includes a carbonnano-fiber material.
 149. A method of producing a proton conductoraccording to claim 139, wherein the halogenated tubular carbonaceousmaterial derivative comprises a fluoride.
 150. A method of producing aproton conductor according to claim 139, further comprising the step ofdispersing the tubular carbonaceous material derivative within a liquid,and filtering the dispersion of the tubular carbonaceous materialderivative so as to form a film.
 151. An electrochemical devicecomprising a first electrode, a second electrode, and a proton conductorthat is positioned between the first and second electrodes, the protonconductor comprising a tubular carbonaceous material derivative thatcomprises a plurality of functional groups so as to be capable oftransferring protons between the functional groups of the tubularcarbonaceous material derivative.
 152. An electrochemical deviceaccording to claim 151, wherein the functional groups comprise —XH whereX is an arbitrary atom or an atomic group that has a bivalent bond andwhere H is a hydrogen atom.
 153. An electrochemical device according toclaim 151, wherein the functional groups comprise —OH or —YOH where Y isan arbitrary atom or an atomic group that has bivalent bond, where O isan oxygen atom and where H is a hydrogen atom.
 154. An electrochemicaldevice according to claim 151, wherein the functional groups areselected from the group consisting of —OH, —OSO₃H, —COOH, —SO₃H, and—OPO(OH)₃.
 155. An electrochemical device according to claim 151,wherein the tubular carbonaceous material derivative further comprises aplurality of electron attractive groups in addition to the functionalgroups.
 156. An electrochemical device according to claim 155, whereinthe electron attractive groups are selected from the group consisting ofnitro groups, carbonyl groups, carboxyl groups, nitrile groups, alkylhalide groups and halogen atoms.
 157. An electrochemical deviceaccording to claim 151, wherein the tubular carbonaceous materialderivative comprises a tubular carbonaceous material that is asingle-wall carbon nano-tube material.
 158. An electrochemical deviceaccording to claim 151, wherein the tubular carbonaceous materialderivative comprises a tubular carbonaceous material that is amulti-wall carbon nano-tube material.
 159. An electrochemical deviceaccording to claim 151, wherein the tubular carbonaceous materialderivative comprises a tubular carbonaceous material that is a carbonnano-fiber material.
 160. An electrochemical device according to claim151, wherein the proton conductor comprises a mixture of the tubularcarbonaceous material derivative and a fullerene derivative that alsoincludes the functional groups.
 161. An electrochemical device accordingto claim 151, wherein the electrochemical device comprises a fuel cell.